HTML 5.3: 10. Rendering

10. Rendering

User agents are not required to present HTML documents in any particular way. However, this section provides a set of suggestions for rendering HTML documents that, if followed, are likely to lead to a user experience that closely resembles the experience intended by the documents' authors. So as to avoid confusion regarding the normativity of this section, "must" has not been used. Instead, the term "expected" is used to indicate behavior that will lead to this experience. For the purposes of conformance for user agents designated as supporting the suggested default rendering, the term "expected" in this section has the same conformance implications as "must".

10.1. Introduction

In general, user agents are expected to support CSS, and many of the suggestions in this section are expressed in CSS terms. User agents that use other presentation mechanisms can derive their expected behavior by translating from the CSS rules given in this section.

In the absence of style-layer rules to the contrary (e.g., author style sheets), user agents are expected to render an element so that it conveys to the user the meaning that the element represents, as described by this specification.

The suggestions in this section generally assume a visual output medium with a resolution of 96dpi or greater, but HTML is intended to apply to multiple media (it is a media-independent language). User agent implementors are encouraged to adapt the suggestions in this section to their target media.

An element is being rendered if it has any associated CSS layout boxes, SVG layout boxes, or some equivalent in other styling languages.

NOTE: Just being off-screen does not mean the element is not being rendered. The presence of the hidden attribute normally means the element is not being rendered, though this might be overridden by the style sheets.

User agents that do not honor author-level CSS style sheets are nonetheless expected to act as if they applied the CSS rules given in these sections in a manner consistent with this specification and the relevant CSS and Unicode specifications. [CSS-2015] [UNICODE] [BIDI]

NOTE: This is especially important for issues relating to the display, unicode-bidi, and direction properties.

10.2. The CSS user agent style sheet and presentational hints

The CSS rules given in these subsections are, except where otherwise specified, expected to be used as part of the user-agent level style sheet defaults for all documents that contain HTML elements.

Some rules are intended for the author-level zero-specificity presentational hints part of the CSS cascade; these are explicitly called out as presentational hints.

When the text below says that an attribute attribute on an element element maps to the pixel length property (or properties) properties, it means that if element has an attribute attribute set, and parsing that attribute’s value using the rules for parsing non-negative integers doesn’t generate an error, then the user agent is expected to use the parsed value as a pixel length for a presentational hint for properties.

When the text below says that an attribute attribute on an element element maps to the dimension property (or properties) properties, it means that if element has an attribute attribute set, and parsing that attribute’s value using the rules for parsing dimension values doesn’t generate an error, then the user agent is expected to use the parsed dimension as the value for a presentational hint for properties, with the value given as a pixel length if the dimension was a length, and with the value given as a percentage if the dimension was a percentage.

When the text below says that an attribute attribute on an element element maps to the dimension property (ignoring zero) (or properties) properties, it means that if element has an attribute attribute set, and parsing that attribute’s value using the rules for parsing non-zero dimension values doesn’t generate an error, then the user agent is expected to use the parsed dimension as the value for a presentational hint for properties, with the value given as a pixel length if the dimension was a length, and with the value given as a percentage if the dimension was a percentage.

When a user agent is to align descendants of a node, the user agent is expected to align only those descendants that have both their margin-inline-start and margin-inline-end properties computing to a value other than auto, that are over-constrained and that have one of those two margins with a used value forced to a greater value, and that do not themselves have an applicable align attribute. When multiple elements are to align a particular descendant, the most deeply nested such element is expected to override the others. Aligned elements are expected to be aligned by having the used values of their margins on the line-left and line-right sides be set accordingly. [CSS-LOGICAL-PROPS] [CSS-WRITING-MODES-3]

10.3. Non-replaced elements

10.3.1. Hidden elements

@namespace url(http://www.w3.org/1999/xhtml);

[hidden], area, base, basefont, datalist, head, link, meta,
noembed, noframes, param, rp, script, source, style, template, track, title {
  display: none;
}

embed[hidden] { display: inline; height: 0; width: 0; }

input[type=hidden i] { display: none !important; }

@media (scripting) {
  noscript { display: none !important; }
}

10.3.2. The page

@namespace url(http://www.w3.org/1999/xhtml);

html, body { display: block; }

For each property in the table below, given a body element, the first attribute that exists maps to the pixel length property on the body element. If none of the attributes for a property are found, or if the value of the attribute that was found cannot be parsed successfully, then a default value of 8px is expected to be used for that property instead.

Property	Source
margin-top	`body` element’s `marginheight` attribute
	The `body` element’s container frame element's `marginheight` attribute
	`body` element’s `topmargin` attribute
margin-right	`body` element’s `marginwidth` attribute
	The `body` element’s container frame element's `marginwidth` attribute
	`body` element’s `rightmargin` attribute
margin-bottom	`body` element’s `marginheight` attribute
	The `body` element’s container frame element's `marginheight` attribute
	`body` element’s `bottommargin` attribute
margin-left	`body` element’s `marginwidth` attribute
	The `body` element’s container frame element's `marginwidth` attribute
	`body` element’s `leftmargin` attribute

If the body element’s node document's browsing context is a nested browsing context, and the browsing context container of that nested browsing context is a frame or iframe element, then the container frame element of the body element is that frame or iframe element. Otherwise, there is no container frame element.

The above requirements imply that a page can change the margins of another page (including one from another origin) using, for example, an iframe. This is potentially a security risk, as it might in some cases allow an attack to contrive a situation in which a page is rendered not as the author intended, possibly for the purposes of phishing or otherwise misleading the user.

If a Document is in a nested browsing context, it is expected to be positioned and sized to fit inside the content box of its browsing context container. If a browsing context's browsing context container is not being rendered, the browsing context is expected to have a viewport with zero width and zero height.

If the Document is in a nested browsing context, and the browsing context container of that nested browsing context is a frame or iframe element, and that element has a scrolling attribute, and that attribute’s value is an ASCII case-insensitive match for the string "off", "noscroll", or "no", then the user agent is expected to prevent any scroll bars from being shown for the viewport of the nested browsing context, regardless of the overflow property that applies to that viewport.

When a body element has a background attribute set to a non-empty value, the new value is expected to be parsed relative to the element’s node document, and if this is successful, the user agent is expected to treat the attribute as a presentational hint setting the element’s background-image property to the resulting URL string.

When a body element has a bgcolor attribute set, the new value is expected to be parsed using the rules for parsing a legacy color value, and if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the element’s background-color property to the resulting color.

When a body element has a text attribute, its value is expected to be parsed using the rules for parsing a legacy color value, and if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the element’s color property to the resulting color.

When a body element has a link attribute, its value is expected to be parsed using the rules for parsing a legacy color value, and if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the color property of any element in the Document matching the :link pseudo-class to the resulting color.

When a body element has a vlink attribute, its value is expected to be parsed using the rules for parsing a legacy color value, and if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the color property of any element in the Document matching the :visited pseudo-class to the resulting color.

When a body element has an alink attribute, its value is expected to be parsed using the rules for parsing a legacy color value, and if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the color property of any element in the Document matching the :active pseudo-class and either the :link pseudo-class or the :visited pseudo-class to the resulting color.

10.3.3. Flow content

@namespace url(http://www.w3.org/1999/xhtml);

address, blockquote, center, div, figure, figcaption, footer, form, header, hr,
legend, listing, main, p, plaintext, pre, xmp {
  display: block;
}

blockquote, figure, listing, p, plaintext, pre, xmp {
  margin-block-start: 1em; margin-block-end: 1em;
}

blockquote, figure { margin-inline-start: 40px; margin-inline-end: 40px; }

address { font-style: italic; }
listing, plaintext, pre, xmp {
  font-family: monospace; white-space: pre;
}

dialog:not([open]) { display: none; }
dialog {
  position: absolute;
  left: 0; right: 0;
  width: fit-content;
  height: fit-content;
  margin: auto;
  border: solid;
  padding: 1em;
  background: white;
  color: black;
}
dialog::backdrop {
  background: rgba(0,0,0,0.1);
}

/* for small devices, modal dialogs go full-screen */
@media screen and (max-width: 540px) {
  dialog:modal {
    top: 0;
    width: auto;
    margin: 1em;
  }
}

slot {
  display: contents;
}

The following rules are also expected to apply, as presentational hints:

@namespace url(http://www.w3.org/1999/xhtml);

pre[wrap] { white-space: pre-wrap; }

In quirks mode, the following rules are also expected to apply:

@namespace url(http://www.w3.org/1999/xhtml);

form { margin-block-end: 1em; }

The center element, and the div element when it has an align attribute whose value is an ASCII case-insensitive match for either the string "center" or the string "middle", are expected to center text within themselves, as if they had their text-align property set to center in a presentational hint, and to align descendants to the center.

The div element, when it has an align attribute whose value is an ASCII case-insensitive match for the string "left", is expected to left-align text within itself, as if it had its text-align property set to left in a presentational hint, and to align descendants to the left.

The div element, when it has an align attribute whose value is an ASCII case-insensitive match for the string "right", is expected to right-align text within itself, as if it had its text-align property set to right in a presentational hint, and to align descendants to the right.

The div element, when it has an align attribute whose value is an ASCII case-insensitive match for the string "justify", is expected to full-justify text within itself, as if it had its text-align property set to justify in a presentational hint, and to align descendants to the left.

10.3.4. Phrasing content

@namespace url(http://www.w3.org/1999/xhtml);

cite, dfn, em, i, var { font-style: italic; }
b, strong { font-weight: bolder; }
code, kbd, samp, tt { font-family: monospace; }
big { font-size: larger; }
small { font-size: smaller; }

sub { vertical-align: sub; }
sup { vertical-align: super; }
sub, sup { line-height: normal; font-size: smaller; }

ruby { display: ruby; }
rt   { display: ruby-text; }

:link { color: #0000EE; }
:visited { color: #551A8B; }
:link:active, :visited:active { color: #FF0000; }
:link, :visited { text-decoration: underline; cursor: pointer; }
a:link[rel~=help], a:visited[rel~=help],
area:link[rel~=help], area:visited[rel~=help] { cursor: help; }

:focus { outline: auto; }

mark { background: yellow; color: black; } /* this color is just a suggestion and can be changed based on implementation feedback */

abbr[title], acronym[title] { text-decoration: dotted underline; }
ins, u { text-decoration: underline; }
del, s, strike { text-decoration: line-through; }
blink { text-decoration: blink; }

q::before { content: open-quote; }
q::after { content: close-quote; }

br { display-outside: newline; } /* this also has bidi implications */
nobr { white-space: nowrap; }
wbr { display-outside: break-opportunity; } /* this also has bidi implications */
nobr wbr { white-space: normal; }

The following rules are also expected to apply, as presentational hints:

@namespace url(http://www.w3.org/1999/xhtml);

br[clear=left i] { clear: left; }
br[clear=right i] { clear: right; }
br[clear=all i], br[clear=both i] { clear: both; }

User agents that do not support correct ruby rendering are expected to render parentheses around the text of rt elements in the absence of rp elements. [CSS3-RUBY]

User agents are expected to support the clear property on inline elements (in order to render br elements with clear attributes) in the manner described in the non-normative note to this effect in the CSS specification.

The initial value for the color property is expected to be black. The initial value for the background-color property is expected to be transparent. The canvas' background is expected to be white.

When a font element has a color attribute, its value is expected to be parsed using the rules for parsing a legacy color value, and if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the element’s color property to the resulting color.

The font element is expected to override the color of any text decoration that spans the text of the element to the used value of the element’s color property.

When a font element has a face attribute, the user agent is expected to treat the attribute as a presentational hint setting the element’s font-family property to the attribute’s value.

When a font element has a size attribute, the user agent is expected to use the following steps, known as the rules for parsing a legacy font size, to treat the attribute as a presentational hint setting the element’s font-size property:

Let input be the attribute’s value.
Let position be a pointer into input, initially pointing at the start of the string.
Skip white space.
If position is past the end of input, there is no presentational hint. Abort these steps.
If the character at position is a U+002B PLUS SIGN character (+), then let mode be relative-plus, and advance position to the next character. Otherwise, if the character at position is a U+002D HYPHEN-MINUS character (-), then let mode be relative-minus, and advance position to the next character. Otherwise, let mode be absolute.
Collect a sequence of characters that are ASCII digits, and let the resulting sequence be digits.
If digits is the empty string, there is no presentational hint. Abort these steps.
Interpret digits as a base-ten integer. Let value be the resulting number.
If mode is relative-plus, then increment value by 3. If mode is relative-minus, then let value be the result of subtracting value from 3.
If value is greater than 7, let it be 7.
If value is less than 1, let it be 1.

Set font-size to the keyword corresponding to the value of value according to the following table:

`value`	font-size keyword	Notes
1	x-small
2	small
3	medium
4	large
5	x-large
6	xx-large
7	xxx-large	see below

The xxx-large value is a non-CSS value used here to indicate a font size 50% larger than xx-large.

10.3.5. Bidirectional text

@namespace url(http://www.w3.org/1999/xhtml);

[dir]:dir(ltr), bdi:dir(ltr), input[type=tel i]:dir(ltr) { direction: ltr; }
[dir]:dir(rtl), bdi:dir(rtl) { direction: rtl; }

address, blockquote, center, div, figure, figcaption, footer, form, header, hr,
legend, listing, main, p, plaintext, pre, summary, xmp, article, aside, h1, h2,
h3, h4, h5, h6, hgroup, nav, section, table, caption, colgroup, col, thead,
tbody, tfoot, tr, td, th, dir, dd, dl, dt, ol, ul, li, bdi, output,
[dir=ltr i], [dir=rtl i], [dir=auto i] {
  unicode-bidi: isolate;
}

bdo, bdo[dir] { unicode-bidi: isolate-override; }

input[dir=auto i]:matches([type=search i], [type=tel i], [type=url i],
[type=email i]), textarea[dir=auto i], pre[dir=auto i] {
  unicode-bidi: plaintext;
}
/* see prose for input elements whose type attribute is in the Text state */

/* the rules setting the 'content' property on <br> and <wbr> elements also has bidi implications */

When an input element’s dir attribute is in the auto state and its type attribute is in the Text state, then the user agent is expected to act as if it had a user-agent-level style sheet rule setting the unicode-bidi property to plaintext.

Input fields (i.e., textarea elements, and input elements when their type attribute is in the Text, Search, Telephone, URL, or E-mail state) are expected to present an editing user interface with a directionality that matches the element’s direction property.

When the document’s character encoding is ISO-8859-8, the following rules are additionally expected to apply, following those above: [ENCODING]

@namespace url(http://www.w3.org/1999/xhtml);

address, blockquote, center, div, figure, figcaption, footer, form, header, hr,
legend, listing, main, p, plaintext, pre, summary, xmp, article, aside, h1, h2,
h3, h4, h5, h6, hgroup, nav, section, table, caption, colgroup, col, thead,
tbody, tfoot, tr, td, th, dir, dd, dl, dt, ol, ul, li, [dir=ltr i],
[dir=rtl i], [dir=auto i], *|* {
  unicode-bidi: bidi-override;
}
input:not([type=submit i]):not([type=reset i]):not([type=button i]),
textarea {
  unicode-bidi: normal;
}

10.3.6. Quotes

This block is generated from the Unicode Common Locale Data Repository. [CLDR]

User agents are expected to use either the block below (which will be regularly updated) or to automatically generate their own copy directly from the source material. The language codes are derived from the CLDR file names. The quotes are derived from the delimiter blocks, with fallback handled as specified in the CLDR documentation.

@namespace url(http://www.w3.org/1999/xhtml);

:root                { quotes: '“' '”' '‘' '’' }
:root:lang(af)       { quotes: '“' '”' '‘' '’' }
:root:lang(agq)      { quotes: '„' '”' '‚' '’' }
:root:lang(ak)       { quotes: '“' '”' '‘' '’' }
:root:lang(am)       { quotes: '«' '»' '‹' '›' }
:root:lang(ar)       { quotes: '”' '“' '’' '‘' }
:root:lang(asa)      { quotes: '“' '”' '‘' '’' }
:root:lang(ast)      { quotes: '«' '»' '“' '”' }
:root:lang(az)       { quotes: '“' '”' '‘' '’' }
:root:lang(az-Cyrl)  { quotes: '«' '»' '‹' '›' }
:root:lang(bas)      { quotes: '«' '»' '„' '“' }
:root:lang(be)       { quotes: '«' '»' '«' '»' }
:root:lang(bem)      { quotes: '“' '”' '‘' '’' }
:root:lang(bez)      { quotes: '“' '”' '‘' '’' }
:root:lang(bg)       { quotes: '„' '“' '„' '“' }
:root:lang(bm)       { quotes: '«' '»' '“' '”' }
:root:lang(bn)       { quotes: '“' '”' '‘' '’' }
:root:lang(br)       { quotes: '«' '»' '“' '”' }
:root:lang(brx)      { quotes: '“' '”' '‘' '’' }
:root:lang(bs)       { quotes: '„' '“' '‘' '’' }
:root:lang(bs-Cyrl)  { quotes: '„' '“' '‚' '‘' }
:root:lang(ca)       { quotes: '«' '»' '“' '”' }
:root:lang(cgg)      { quotes: '“' '”' '‘' '’' }
:root:lang(chr)      { quotes: '“' '”' '‘' '’' }
:root:lang(cs)       { quotes: '„' '“' '‚' '‘' }
:root:lang(cy)       { quotes: '‘' '’' '“' '”' }
:root:lang(da)       { quotes: '“' '”' '‘' '’' }
:root:lang(dav)      { quotes: '“' '”' '‘' '’' }
:root:lang(de)       { quotes: '„' '“' '‚' '‘' }
:root:lang(dje)      { quotes: '“' '”' '‘' '’' }
:root:lang(dsb)      { quotes: '„' '“' '‚' '‘' }
:root:lang(dua)      { quotes: '«' '»' '‘' '’' }
:root:lang(dyo)      { quotes: '«' '»' '“' '”' }
:root:lang(dz)       { quotes: '“' '”' '‘' '’' }
:root:lang(ebu)      { quotes: '“' '”' '‘' '’' }
:root:lang(ee)       { quotes: '“' '”' '‘' '’' }
:root:lang(el)       { quotes: '«' '»' '“' '”' }
:root:lang(en)       { quotes: '“' '”' '‘' '’' }
:root:lang(es)       { quotes: '«' '»' '“' '”' }
:root:lang(et)       { quotes: '„' '“' '‚' '‘' }
:root:lang(eu)       { quotes: '“' '”' '“' '”' }
:root:lang(ewo)      { quotes: '«' '»' '“' '”' }
:root:lang(fa)       { quotes: '«' '»' '‹' '›' }
:root:lang(ff)       { quotes: '„' '”' '‚' '’' }
:root:lang(fi)       { quotes: '”' '”' '’' '’' }
:root:lang(fil)      { quotes: '“' '”' '‘' '’' }
:root:lang(fo)       { quotes: '“' '”' '‘' '’' }
:root:lang(fr)       { quotes: '«' '»' '«' '»' }
:root:lang(fr-CH)    { quotes: '«' '»' '‹' '›' }
:root:lang(ga)       { quotes: '“' '”' '‘' '’' }
:root:lang(gd)       { quotes: '“' '”' '‘' '’' }
:root:lang(gl)       { quotes: '“' '”' '‘' '’' }
:root:lang(gsw)      { quotes: '«' '»' '‹' '›' }
:root:lang(gu)       { quotes: '“' '”' '‘' '’' }
:root:lang(guz)      { quotes: '“' '”' '‘' '’' }
:root:lang(ha)       { quotes: '“' '”' '‘' '’' }
:root:lang(he)       { quotes: '”' '”' '’' '’' }
:root:lang(hi)       { quotes: '“' '”' '‘' '’' }
:root:lang(hr)       { quotes: '„' '“' '‚' '‘' }
:root:lang(hsb)      { quotes: '„' '“' '‚' '‘' }
:root:lang(hu)       { quotes: '„' '”' '»' '«' }
:root:lang(hy)       { quotes: '«' '»' '«' '»' }
:root:lang(id)       { quotes: '“' '”' '‘' '’' }
:root:lang(ig)       { quotes: '“' '”' '‘' '’' }
:root:lang(is)       { quotes: '„' '“' '‚' '‘' }
:root:lang(it)       { quotes: '«' '»' '“' '”' }
:root:lang(ja)       { quotes: '「' '」' '『' '』' }
:root:lang(jgo)      { quotes: '«' '»' '‹' '›' }
:root:lang(jmc)      { quotes: '“' '”' '‘' '’' }
:root:lang(ka)       { quotes: '„' '“' '«' '»' }
:root:lang(kab)      { quotes: '«' '»' '“' '”' }
:root:lang(kam)      { quotes: '“' '”' '‘' '’' }
:root:lang(kde)      { quotes: '“' '”' '‘' '’' }
:root:lang(kea)      { quotes: '“' '”' '‘' '’' }
:root:lang(khq)      { quotes: '“' '”' '‘' '’' }
:root:lang(ki)       { quotes: '“' '”' '‘' '’' }
:root:lang(kk)       { quotes: '«' '»' '“' '”' }
:root:lang(kkj)      { quotes: '«' '»' '‹' '›' }
:root:lang(kln)      { quotes: '“' '”' '‘' '’' }
:root:lang(km)       { quotes: '“' '”' '‘' '’' }
:root:lang(kn)       { quotes: '“' '”' '‘' '’' }
:root:lang(ko)       { quotes: '“' '”' '‘' '’' }
:root:lang(ksb)      { quotes: '“' '”' '‘' '’' }
:root:lang(ksf)      { quotes: '«' '»' '‘' '’' }
:root:lang(ky)       { quotes: '«' '»' '„' '“' }
:root:lang(lag)      { quotes: '”' '”' '’' '’' }
:root:lang(lb)       { quotes: '„' '“' '‚' '‘' }
:root:lang(lg)       { quotes: '“' '”' '‘' '’' }
:root:lang(ln)       { quotes: '“' '”' '‘' '’' }
:root:lang(lo)       { quotes: '“' '”' '‘' '’' }
:root:lang(lrc)      { quotes: '“' '”' '‘' '’' }
:root:lang(lt)       { quotes: '„' '“' '„' '“' }
:root:lang(lu)       { quotes: '“' '”' '‘' '’' }
:root:lang(luo)      { quotes: '“' '”' '‘' '’' }
:root:lang(luy)      { quotes: '„' '“' '‚' '‘' }
:root:lang(lv)       { quotes: '“' '”' '‘' '’' }
:root:lang(mas)      { quotes: '“' '”' '‘' '’' }
:root:lang(mer)      { quotes: '“' '”' '‘' '’' }
:root:lang(mfe)      { quotes: '“' '”' '‘' '’' }
:root:lang(mg)       { quotes: '«' '»' '“' '”' }
:root:lang(mgo)      { quotes: '“' '”' '‘' '’' }
:root:lang(mk)       { quotes: '„' '“' '‚' '‘' }
:root:lang(ml)       { quotes: '“' '”' '‘' '’' }
:root:lang(mn)       { quotes: '“' '”' '‘' '’' }
:root:lang(mr)       { quotes: '“' '”' '‘' '’' }
:root:lang(ms)       { quotes: '“' '”' '‘' '’' }
:root:lang(mt)       { quotes: '“' '”' '‘' '’' }
:root:lang(mua)      { quotes: '«' '»' '“' '”' }
:root:lang(my)       { quotes: '“' '”' '‘' '’' }
:root:lang(mzn)      { quotes: '«' '»' '‹' '›' }
:root:lang(naq)      { quotes: '“' '”' '‘' '’' }
:root:lang(nb)       { quotes: '«' '»' '‘' '’' }
:root:lang(nd)       { quotes: '“' '”' '‘' '’' }
:root:lang(ne)       { quotes: '“' '”' '‘' '’' }
:root:lang(nl)       { quotes: '‘' '’' '“' '”' }
:root:lang(nmg)      { quotes: '„' '”' '«' '»' }
:root:lang(nn)       { quotes: '«' '»' '‘' '’' }
:root:lang(nnh)      { quotes: '«' '»' '“' '”' }
:root:lang(nus)      { quotes: '“' '”' '‘' '’' }
:root:lang(nyn)      { quotes: '“' '”' '‘' '’' }
:root:lang(pa)       { quotes: '“' '”' '‘' '’' }
:root:lang(pl)       { quotes: '„' '”' '«' '»' }
:root:lang(pt)       { quotes: '“' '”' '‘' '’' }
:root:lang(pt-PT)    { quotes: '«' '»' '“' '”' }
:root:lang(rn)       { quotes: '”' '”' '’' '’' }
:root:lang(ro)       { quotes: '„' '”' '«' '»' }
:root:lang(rof)      { quotes: '“' '”' '‘' '’' }
:root:lang(ru)       { quotes: '«' '»' '„' '“' }
:root:lang(rw)       { quotes: '«' '»' '‘' '’' }
:root:lang(rwk)      { quotes: '“' '”' '‘' '’' }
:root:lang(saq)      { quotes: '“' '”' '‘' '’' }
:root:lang(sbp)      { quotes: '“' '”' '‘' '’' }
:root:lang(seh)      { quotes: '“' '”' '‘' '’' }
:root:lang(ses)      { quotes: '“' '”' '‘' '’' }
:root:lang(sg)       { quotes: '«' '»' '“' '”' }
:root:lang(shi)      { quotes: '«' '»' '„' '”' }
:root:lang(shi-Latn) { quotes: '«' '»' '„' '”' }
:root:lang(si)       { quotes: '“' '”' '‘' '’' }
:root:lang(sk)       { quotes: '„' '“' '‚' '‘' }
:root:lang(sl)       { quotes: '„' '“' '‚' '‘' }
:root:lang(sn)       { quotes: '”' '”' '’' '’' }
:root:lang(so)       { quotes: '“' '”' '‘' '’' }
:root:lang(sq)       { quotes: '«' '»' '“' '”' }
:root:lang(sr)       { quotes: '„' '“' '‘' '‘' }
:root:lang(sr-Latn)  { quotes: '„' '“' '‘' '‘' }
:root:lang(sv)       { quotes: '”' '”' '’' '’' }
:root:lang(sw)       { quotes: '“' '”' '‘' '’' }
:root:lang(ta)       { quotes: '“' '”' '‘' '’' }
:root:lang(te)       { quotes: '“' '”' '‘' '’' }
:root:lang(teo)      { quotes: '“' '”' '‘' '’' }
:root:lang(th)       { quotes: '“' '”' '‘' '’' }
:root:lang(ti-ER)    { quotes: '‘' '’' '“' '”' }
:root:lang(tk)       { quotes: '“' '”' '“' '”' }
:root:lang(to)       { quotes: '“' '”' '‘' '’' }
:root:lang(tr)       { quotes: '“' '”' '‘' '’' }
:root:lang(twq)      { quotes: '“' '”' '‘' '’' }
:root:lang(tzm)      { quotes: '“' '”' '‘' '’' }
:root:lang(uk)       { quotes: '«' '»' '„' '“' }
:root:lang(ur)       { quotes: '”' '“' '’' '‘' }
:root:lang(uz)       { quotes: '“' '”' '’' '‘' }
:root:lang(uz-Cyrl)  { quotes: '“' '”' '‘' '’' }
:root:lang(vai)      { quotes: '“' '”' '‘' '’' }
:root:lang(vai-Latn) { quotes: '“' '”' '‘' '’' }
:root:lang(vi)       { quotes: '“' '”' '‘' '’' }
:root:lang(vun)      { quotes: '“' '”' '‘' '’' }
:root:lang(xog)      { quotes: '“' '”' '‘' '’' }
:root:lang(yav)      { quotes: '«' '»' '«' '»' }
:root:lang(yo)       { quotes: '“' '”' '‘' '’' }
:root:lang(yo-BJ)    { quotes: '“' '”' '‘' '’' }
:root:lang(yue)      { quotes: '「' '」' '『' '』' }
:root:lang(zgh)      { quotes: '«' '»' '„' '”' }
:root:lang(zh)       { quotes: '“' '”' '‘' '’' }
:root:lang(zh-Hant)  { quotes: '「' '」' '『' '』' }
:root:lang(zu)       { quotes: '“' '”' '‘' '’' }

10.3.6.1. Multilingual documents

Quotes have the delimiter set to that of the source language, not the quoted language.

In this example, the source language is English and the language being quoted is Japanese:

<p lang="en">She said <q lang="ja">こんにちは</q></p>

This should render as:

She said “こんにちは”

It should not render with Japanese quote marks

She said 「こんにちは」

10.3.7. Sections and headings

@namespace url(http://www.w3.org/1999/xhtml);

article, aside, h1, h2, h3, h4, h5, h6, hgroup, nav, section {
  display: block;
}

h1 { margin-block-start: 0.67em; margin-block-end: 0.67em; font-size: 2.00em; font-weight: bold; }
h2 { margin-block-start: 0.83em; margin-block-end: 0.83em; font-size: 1.50em; font-weight: bold; }
h3 { margin-block-start: 1.00em; margin-block-end: 1.00em; font-size: 1.17em; font-weight: bold; }
h4 { margin-block-start: 1.33em; margin-block-end: 1.33em; font-size: 1.00em; font-weight: bold; }
h5 { margin-block-start: 1.67em; margin-block-end: 1.67em; font-size: 0.83em; font-weight: bold; }
h6 { margin-block-start: 2.33em; margin-block-end: 2.33em; font-size: 0.67em; font-weight: bold; }

In the following CSS block, x is shorthand for the following selector: :matches(article, aside, nav, section)

@namespace url(http://www.w3.org/1999/xhtml);

x h1 { margin-block-start: 0.83em; margin-block-end: 0.83em; font-size: 1.50em; }
x x h1 { margin-block-start: 1.00em; margin-block-end: 1.00em; font-size: 1.17em; }
x x x h1 { margin-block-start: 1.33em; margin-block-end: 1.33em; font-size: 1.00em; }
x x x x h1 { margin-block-start: 1.67em; margin-block-end: 1.67em; font-size: 0.83em; }
x x x x x h1 { margin-block-start: 2.33em; margin-block-end: 2.33em; font-size: 0.67em; }

x hgroup > h1 ~ h2 { margin-block-start: 1.00em; margin-block-end: 1.00em; font-size: 1.17em; }
x x hgroup > h1 ~ h2 { margin-block-start: 1.33em; margin-block-end: 1.33em; font-size: 1.00em; }
x x x hgroup > h1 ~ h2 { margin-block-start: 1.67em; margin-block-end: 1.67em; font-size: 0.83em; }
x x x x hgroup > h1 ~ h2 { margin-block-start: 2.33em; margin-block-end: 2.33em; font-size: 0.67em; }

x hgroup > h1 ~ h3 { margin-block-start: 1.33em; margin-block-end: 1.33em; font-size: 1.00em; }
x x hgroup > h1 ~ h3 { margin-block-start: 1.67em; margin-block-end: 1.67em; font-size: 0.83em; }
x x x hgroup > h1 ~ h3 { margin-block-start: 2.33em; margin-block-end: 2.33em; font-size: 0.67em; }

x hgroup > h1 ~ h4 { margin-block-start: 1.67em; margin-block-end: 1.67em; font-size: 0.83em; }
x x hgroup > h1 ~ h4 { margin-block-start: 2.33em; margin-block-end: 2.33em; font-size: 0.67em; }

x hgroup > h1 ~ h5 { margin-block-start: 2.33em; margin-block-end: 2.33em; font-size: 0.67em; }

NOTE: The shorthand is used to keep this block at least mildly readable.

10.3.8. Lists

@namespace url(http://www.w3.org/1999/xhtml);

dir, dd, dl, dt, ol, ul { display: block; }
li { display: list-item; }

dir, dl, ol, ul { margin-block-start: 1em; margin-block-end: 1em; }

:matches(dir, dl, ol, ul) :matches(dir, dl, ol, ul) {
  margin-block-start: 0; margin-block-end: 0;
}

dd { margin-inline-start: 40px; }
dir, ol, ul { padding-inline-start: 40px; }

ol { list-style-type: decimal; }

dir, ul {
  list-style-type: disc;
}
:matches(dir, ol, ul) :matches(dir, ul) {
  list-style-type: circle;
}
:matches(dir, ol, ul) :matches(dir, ol, ul) :matches(dir, ul) {
  list-style-type: square;
}

The following rules are also expected to apply, as presentational hints:

@namespace url(http://www.w3.org/1999/xhtml);

ol[type=1], li[type=1] { list-style-type: decimal; }
ol[type=a], li[type=a] { list-style-type: lower-alpha; }
ol[type=A], li[type=A] { list-style-type: upper-alpha; }
ol[type=i], li[type=i] { list-style-type: lower-roman; }
ol[type=I], li[type=I] { list-style-type: upper-roman; }
ul[type=none i], li[type=none i] { list-style-type: none; }
ul[type=disc i], li[type=disc i] { list-style-type: disc; }
ul[type=circle i], li[type=circle i] { list-style-type: circle; }
ul[type=square i], li[type=square i] { list-style-type: square; }

In the above stylesheet, the attribute selectors for the ol and li elements are expected to be treated as case-sensitive.

When rendering li elements, non-CSS user agents are expected to use the ordinal value of the li element to render the counter in the list item marker.

This specification does not yet define the CSS-specific rules for rendering li elements, because CSS doesn’t yet provide sufficient hooks for this purpose.

10.3.9. Tables

@namespace url(http://www.w3.org/1999/xhtml);

table { display: table; }
caption { display: table-caption; }
colgroup, colgroup[hidden] { display: table-column-group; }
col, col[hidden] { display: table-column; }
thead, thead[hidden] { display: table-header-group; }
tbody, tbody[hidden] { display: table-row-group; }
tfoot, tfoot[hidden] { display: table-footer-group; }
tr, tr[hidden] { display: table-row; }
td, th, td[hidden], th[hidden] { display: table-cell; }

colgroup[hidden], col[hidden], thead[hidden], tbody[hidden],
tfoot[hidden], tr[hidden], td[hidden], th[hidden] {
  visibility: collapse;
}

table {
  box-sizing: border-box;
  border-spacing: 2px;
  border-collapse: separate;
  text-indent: initial;
}
td, th { padding: 1px; }
th { font-weight: bold; }
caption { text-align: center; }
thead, tbody, tfoot, table > tr { vertical-align: middle; }
tr, td, th { vertical-align: inherit; }

table, td, th { border-color: gray; }
thead, tbody, tfoot, tr { border-color: inherit; }
table[rules=none i], table[rules=groups i], table[rules=rows i],
table[rules=cols i], table[rules=all i], table[frame=void i],
table[frame=above i], table[frame=below i], table[frame=hsides i],
table[frame=lhs i], table[frame=rhs i], table[frame=vsides i],
table[frame=box i], table[frame=border i],
table[rules=none i] > tr > td, table[rules=none i] > tr > th,
table[rules=groups i] > tr > td, table[rules=groups i] > tr > th,
table[rules=rows i] > tr > td, table[rules=rows i] > tr > th,
table[rules=cols i] > tr > td, table[rules=cols i] > tr > th,
table[rules=all i] > tr > td, table[rules=all i] > tr > th,
table[rules=none i] > thead > tr > td, table[rules=none i] > thead > tr > th,
table[rules=groups i] > thead > tr > td, table[rules=groups i] > thead > tr > th,
table[rules=rows i] > thead > tr > td, table[rules=rows i] > thead > tr > th,
table[rules=cols i] > thead > tr > td, table[rules=cols i] > thead > tr > th,
table[rules=all i] > thead > tr > td, table[rules=all i] > thead > tr > th,
table[rules=none i] > tbody > tr > td, table[rules=none i] > tbody > tr > th,
table[rules=groups i] > tbody > tr > td, table[rules=groups i] > tbody > tr > th,
table[rules=rows i] > tbody > tr > td, table[rules=rows i] > tbody > tr > th,
table[rules=cols i] > tbody > tr > td, table[rules=cols i] > tbody > tr > th,
table[rules=all i] > tbody > tr > td, table[rules=all i] > tbody > tr > th,
table[rules=none i] > tfoot > tr > td, table[rules=none i] > tfoot > tr > th,
table[rules=groups i] > tfoot > tr > td, table[rules=groups i] > tfoot > tr > th,
table[rules=rows i] > tfoot > tr > td, table[rules=rows i] > tfoot > tr > th,
table[rules=cols i] > tfoot > tr > td, table[rules=cols i] > tfoot > tr > th,
table[rules=all i] > tfoot > tr > td, table[rules=all i] > tfoot > tr > th {
  border-color: black;
}

The following rules are also expected to apply, as presentational hints:

@namespace url(http://www.w3.org/1999/xhtml);

table[align=left i] { float: left; }
table[align=right i] { float: right; }
table[align=center i] { margin-inline-start: auto; margin-inline-end: auto; }
thead[align=absmiddle i], tbody[align=absmiddle i], tfoot[align=absmiddle i],
tr[align=absmiddle i], td[align=absmiddle i], th[align=absmiddle i] {
  text-align: center;
}

caption[align=bottom i] { caption-side: bottom; }
p[align=left i], h1[align=left i], h2[align=left i], h3[align=left i],
h4[align=left i], h5[align=left i], h6[align=left i] {
  text-align: left;
}
p[align=right i], h1[align=right i], h2[align=right i], h3[align=right i],
h4[align=right i], h5[align=right i], h6[align=right i] {
  text-align: right;
}
p[align=center i], h1[align=center i], h2[align=center i], h3[align=center i],
h4[align=center i], h5[align=center i], h6[align=center i] {
  text-align: center;
}
p[align=justify i], h1[align=justify i], h2[align=justify i], h3[align=justify i],
h4[align=justify i], h5[align=justify i], h6[align=justify i] {
  text-align: justify;
}
thead[valign=top i], tbody[valign=top i], tfoot[valign=top i],
tr[valign=top i], td[valign=top i], th[valign=top i] {
  vertical-align: top;
}
thead[valign=middle i], tbody[valign=middle i], tfoot[valign=middle i],
tr[valign=middle i], td[valign=middle i], th[valign=middle i] {
  vertical-align: middle;
}
thead[valign=bottom i], tbody[valign=bottom i], tfoot[valign=bottom i],
tr[valign=bottom i], td[valign=bottom i], th[valign=bottom i] {
  vertical-align: bottom;
}
thead[valign=baseline i], tbody[valign=baseline i], tfoot[valign=baseline i],
tr[valign=baseline i], td[valign=baseline i], th[valign=baseline i] {
  vertical-align: baseline;
}

td[nowrap], th[nowrap] { white-space: nowrap; }

table[rules=none i], table[rules=groups i], table[rules=rows i],
table[rules=cols i], table[rules=all i] {
  border-style: hidden;
  border-collapse: collapse;
}
table[border] { border-style: outset; } /* only if border is not equivalent to zero */
table[frame=void i] { border-style: hidden; }
table[frame=above i] { border-style: outset hidden hidden hidden; }
table[frame=below i] { border-style: hidden hidden outset hidden; }
table[frame=hsides i] { border-style: outset hidden outset hidden; }
table[frame=lhs i] { border-style: hidden hidden hidden outset; }
table[frame=rhs i] { border-style: hidden outset hidden hidden; }
table[frame=vsides i] { border-style: hidden outset; }
table[frame=box i], table[frame=border i] { border-style: outset; }

table[border] > tr > td, table[border] > tr > th,
table[border] > thead > tr > td, table[border] > thead > tr > th,
table[border] > tbody > tr > td, table[border] > tbody > tr > th,
table[border] > tfoot > tr > td, table[border] > tfoot > tr > th {
  /* only if border is not equivalent to zero */
  border-width: 1px;
  border-style: inset;
}
table[rules=none i] > tr > td, table[rules=none i] > tr > th,
table[rules=none i] > thead > tr > td, table[rules=none i] > thead > tr > th,
table[rules=none i] > tbody > tr > td, table[rules=none i] > tbody > tr > th,
table[rules=none i] > tfoot > tr > td, table[rules=none i] > tfoot > tr > th,
table[rules=groups i] > tr > td, table[rules=groups i] > tr > th,
table[rules=groups i] > thead > tr > td, table[rules=groups i] > thead > tr > th,
table[rules=groups i] > tbody > tr > td, table[rules=groups i] > tbody > tr > th,
table[rules=groups i] > tfoot > tr > td, table[rules=groups i] > tfoot > tr > th,
table[rules=rows i] > tr > td, table[rules=rows i] > tr > th,
table[rules=rows i] > thead > tr > td, table[rules=rows i] > thead > tr > th,
table[rules=rows i] > tbody > tr > td, table[rules=rows i] > tbody > tr > th,
table[rules=rows i] > tfoot > tr > td, table[rules=rows i] > tfoot > tr > th {
  border-width: 1px;
  border-style: none;
}
table[rules=cols i] > tr > td, table[rules=cols i] > tr > th,
table[rules=cols i] > thead > tr > td, table[rules=cols i] > thead > tr > th,
table[rules=cols i] > tbody > tr > td, table[rules=cols i] > tbody > tr > th,
table[rules=cols i] > tfoot > tr > td, table[rules=cols i] > tfoot > tr > th {
  border-width: 1px;
  block-start-style: none;
  border-inline-end-style: solid;
  border-block-end-style: none;
  border-inline-start-style: solid;
}
table[rules=all i] > tr > td, table[rules=all i] > tr > th,
table[rules=all i] > thead > tr > td, table[rules=all i] > thead > tr > th,
table[rules=all i] > tbody > tr > td, table[rules=all i] > tbody > tr > th,
table[rules=all i] > tfoot > tr > td, table[rules=all i] > tfoot > tr > th {
  border-width: 1px;
  border-style: solid;
}

table[rules=groups i] > colgroup {
  border-inline-start-width: 1px;
  border-inline-start-style: solid;
  border-inline-end-width: 1px;
  border-inline-end-style: solid;
}
table[rules=groups i] > thead,
table[rules=groups i] > tbody,
table[rules=groups i] > tfoot {
  border-block-start-width: 1px;
  border-block-start-style: solid;
  border-block-end-width: 1px;
  border-block-end-style: solid;
}

table[rules=rows i] > tr, table[rules=rows i] > thead > tr,
table[rules=rows i] > tbody > tr, table[rules=rows i] > tfoot > tr {
  border-block-start-width: 1px;
  border-block-start-style: solid;
  border-block-end-width: 1px;
  border-block-end-style: solid;
}

In quirks mode, the following rules are also expected to apply:

@namespace url(http://www.w3.org/1999/xhtml);

table {
  font-weight: initial;
  font-style: initial;
  font-variant: initial;
  font-size: initial;
  line-height: initial;
  white-space: initial;
  text-align: initial;
}

For the purposes of the CSS table model, the col element is expected to be treated as if it was present as many times as its span attribute specifies.

For the purposes of the CSS table model, the colgroup element, if it contains no col element, is expected to be treated as if it had as many such children as its span attribute specifies.

For the purposes of the CSS table model, the colspan and rowspan attributes on td and th elements are expected to provide the special knowledge regarding cells spanning rows and columns.

In HTML documents, the following rules are also expected to apply:

@namespace url(http://www.w3.org/1999/xhtml);

:matches(table, thead, tbody, tfoot, tr) > form { display: none !important; }

The table element’s cellspacing attribute maps to the pixel length property border-spacing on the element.

The table element’s cellpadding attribute maps to the pixel length properties padding-top, padding-right, padding-bottom, and padding-left of any td and th elements that have corresponding cells in the table corresponding to the table element.

The table element’s height attribute maps to the dimension property (ignoring zero) height on the table element.

The table element’s width attribute maps to the dimension property (ignoring zero) width on the table element.

The col element’s width attribute maps to the dimension property (ignoring zero) width on the col element.

The tr element’s height attribute maps to the dimension property (ignoring zero) height on the tr element.

The td and th elements' height attributes map to the dimension property (ignoring zero) height on the element.

The td and th elements' width attributes map to the dimension property (ignoring zero) width on the element.

The thead, tbody, tfoot, tr, td, and th elements when they have an align attribute whose value is an ASCII case-insensitive match for either the string "center" or the string "middle", are expected to center text within themselves, as if they had their text-align property set to text-align: center in a presentational hint, and to align descendants to the center.

The thead, tbody, tfoot, tr, td, and th elements, when they have an align attribute whose value is an ASCII case-insensitive match for the string "left", are expected to left-align text within themselves, as if they had their text-align property set to text-align: left in a presentational hint, and to align descendants to the left.

The thead, tbody, tfoot, tr, td, and th elements, when they have an align attribute whose value is an ASCII case-insensitive match for the string "right", are expected to right-align text within themselves, as if they had their text-align property set to text-align: right in a presentational hint, and to align descendants to the right.

The thead, tbody, tfoot, tr, td, and th elements, when they have an align attribute whose value is an ASCII case-insensitive match for the string "justify", are expected to full-justify text within themselves, as if they had their text-align property set to text-align: justify in a presentational hint, and to align descendants to the left.

User agents are expected to have a rule in their user agent stylesheet that matches th elements that have a parent node whose computed value for the text-align property is its initial value, whose declaration block consists of just a single declaration that sets the text-align property to the value text-align: center.

When a table, thead, tbody, tfoot, tr, td, or th element has a background attribute set to a non-empty value, the new value is expected to be parsed relative to the element’s node document, and if this is successful, the user agent is expected to treat the attribute as a presentational hint setting the element’s background-image property to the resulting URL string.

When a table, thead, tbody, tfoot, tr, td, or th element has a bgcolor attribute set, the new value is expected to be parsed using the rules for parsing a legacy color value, and if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the element’s background-color property to the resulting color.

When a table element has a bordercolor attribute, its value is expected to be parsed using the rules for parsing a legacy color value, and if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the element’s border-top-color, border-right-color, border-bottom-color, and border-left-color properties to the resulting color.

The table element’s border attribute maps to the pixel length properties border-top-width, border-right-width, border-bottom-width, border-left-width on the element. If the attribute is present but parsing the attribute’s value using the rules for parsing non-negative integers generates an error, a default value of 1px is expected to be used for that property instead.

Rules marked "only if border is not equivalent to zero" in the CSS block above is expected to only be applied if the border attribute mentioned in the selectors for the rule is not only present but, when parsed using the rules for parsing non-negative integers, is also found to have a value other than zero or to generate an error.

In quirks mode, a td element or a th element that has a nowrap attribute but also has a width attribute whose value, when parsed using the rules for parsing non-zero dimension values, is found to be a length (not an error or a number classified as a percentage), is expected to have a presentational hint setting the element’s white-space property to white-space: normal, overriding the rule in the CSS block above that sets it to white-space: nowrap.

10.3.10. Margin collapsing quirks

A node is substantial if it is a text node that is not inter-element white space, or if it is an element node.

A node is blank if it is an element that contains no substantial nodes.

The elements with default margins are the following elements: blockquote, dir, dl, h1, h2, h3, h4, h5, h6, listing, ol, p, plaintext, pre, ul, xmp

In quirks mode, any element with default margins that is the child of a body, td, or th element and has no substantial previous siblings is expected to have a user-agent level style sheet rule that sets its margin-block-start property to zero.

In quirks mode, any element with default margins that is the child of a body, td, or th element, has no substantial previous siblings, and is blank, is expected to have a user-agent level style sheet rule that sets its margin-block-end property to zero also.

In quirks mode, any element with default margins that is the child of a td or th element, has no substantial following siblings, and is blank, is expected to have a user-agent level style sheet rule that sets its margin-block-start property to zero.

In quirks mode, any p element that is the child of a td or th element and has no substantial following siblings, is expected to have a user-agent level style sheet rule that sets its margin-block-end property to zero.

10.3.11. Form controls

@namespace url(http://www.w3.org/1999/xhtml);

input, select, option, optgroup, button, textarea {
  text-indent: initial;
}

input:matches([type=radio i], [type=checkbox i], [type=reset i], [type=button i],
[type=submit i], [type=search i]), select, button {
  box-sizing: border-box;
}

textarea { white-space: pre-wrap; }

In quirks mode, the following rules are also expected to apply:

@namespace url(http://www.w3.org/1999/xhtml);

input:not([type=image i]), textarea { box-sizing: border-box; }

Each kind of form control is also described in the Widgets section, which describes the look and feel of the control.

10.3.12. The `hr` element

@namespace url(http://www.w3.org/1999/xhtml);

hr {
  color: gray;
  border-style: inset;
  border-width: 1px;
  margin-block-start: 0.5em;
  margin-inline-end: auto;
  margin-block-end: 0.5em;
  margin-inline-start: auto;
}

The following rules are also expected to apply, as presentational hints:

@namespace url(http://www.w3.org/1999/xhtml);

hr[align=left i] { margin-left: 0; margin-right: auto; }
hr[align=right i] { margin-left: auto; margin-right: 0; }
hr[align=center i] { margin-left: auto; margin-right: auto; }
hr[color], hr[noshade] { border-style: solid; }

If an hr element has either a color attribute or a noshade attribute, and furthermore also has a size attribute, and parsing that attribute’s value using the rules for parsing non-negative integers doesn’t generate an error, then the user agent is expected to use the parsed value divided by two as a pixel length for presentational hints for the properties border-top-width, border-right-width, border-bottom-width, and border-left-width on the element.

Otherwise, if an hr element has neither a color attribute nor a noshade attribute, but does have a size attribute, and parsing that attribute’s value using the rules for parsing non-negative integers doesn’t generate an error, then: if the parsed value is one, then the user agent is expected to use the attribute as a presentational hint setting the element’s border-bottom-width to 0; otherwise, if the parsed value is greater than one, then the user agent is expected to use the parsed value minus two as a pixel length for presentational hints for the height property on the element.

The width attribute on an hr element maps to the dimension property width on the element.

When an hr element has a color attribute, its value is expected to be parsed using the rules for parsing a legacy color value, and if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the element’s color property to the resulting color.

10.3.13. The `fieldset` and `legend` elements

@namespace url(http://www.w3.org/1999/xhtml);

fieldset {
  display: block;
  margin-inline-start: 2px;
  margin-inline-end: 2px;
  border: groove 2px ThreeDFace;
  padding-block-start: 0.35em;
  padding-inline-end: 0.625em;
  padding-block-end: 0.75em;
  padding-inline-start: 0.625em;
  min-width: min-content;
}

legend {
  padding-inline-start: 2px; padding-inline-end: 2px;
}

The fieldset element is expected to establish a new block formatting context.

If the fieldset element has a child that matches the conditions in the list below, then the first such child is the fieldset element’s rendered legend:

The child is a legend element.
The child is not out-of-flow (e.g., not absolutely positioned or floated).
The child is generating a box (e.g., it is not 'display: none' or 'display: contents').

A fieldset element’s rendered legend, if any, is expected to be rendered over the block-start border edge of the fieldset element as a block box (overriding any explicit display value). In the absence of an explicit inline size, the box should shrink-wrap. If the legend element in question has an align attribute, and its value is an ASCII case-insensitive match for one of the strings in the first column of the following table, then the legend is expected to be rendered aligned in the inline direction over the border edge in the position given in the corresponding cell on the same row in the second column. If the attribute is absent or has a value that doesn’t match any of the cases in the table, then the position is expected to be on the right if the direction property on this element has a computed value of rtl, and on the inline-start side. [CSS-WRITING-MODES-3]

Attribute value	Alignment position
`left`	On the inline-left side
`right`	On the inline-right side
`center`	In the middle

10.4. Replaced elements

10.4.1. Embedded content

The embed, iframe, and video elements are expected to be treated as replaced elements.

A canvas element that represents embedded content is expected to be treated as a replaced element; the contents of such elements are the element’s bitmap, if any, or else a transparent black bitmap with the same intrinsic dimensions as the element. Other canvas elements are expected to be treated as ordinary elements in the rendering model.

An object element that represents an image, plugin, or nested browsing context is expected to be treated as a replaced element. Other object elements are expected to be treated as ordinary elements in the rendering model.

An applet element that represents a plugin is expected to be treated as a replaced element. Other applet elements are expected to be treated as ordinary elements in the rendering model.

The audio element, when it is exposing a user interface, is expected to be treated as a replaced element about one line high, as wide as is necessary to expose the user agent’s user interface features. When an audio element is not exposing a user interface, the user agent is expected to force its display property to compute to none, irrespective of CSS rules.

Whether a video element is exposing a user interface is not expected to affect the size of the rendering; controls are expected to be overlaid above the page content without causing any layout changes, and are expected to disappear when the user does not need them.

When a video element represents a poster frame or frame of video, the poster frame or frame of video is expected to be rendered at the largest size that maintains the aspect ratio of that poster frame or frame of video without being taller or wider than the video element itself, and is expected to be centered in the video element.

Any subtitles or captions are expected to be overlayed directly on top of their video element, as defined by the relevant rendering rules; for WebVTT, those are the rules for updating the display of WebVTT text tracks. [WEBVTT]

When the user agent starts exposing a user interface for a video element, the user agent should run the rules for updating the text track rendering of each of the text tracks in the video element’s list of text tracks that are showing and whose text track kind is one of subtitles or captions (e.g., for text tracks based on WebVTT, the rules for updating the display of WebVTT text tracks). [WEBVTT]

Note: Resizing video and canvas elements does not interrupt video playback or clear the canvas.

The following CSS rules are expected to apply:

@namespace url(http://www.w3.org/1999/xhtml);

iframe { border: 2px inset; }
video { object-fit: contain; }

10.4.2. Images

User agents are expected to render img elements and input elements whose type attributes are in the Image Button state, according to the first applicable rules from the following list:

If the element represents an image: The user agent is expected to treat the element as a replaced element and render the image according to the rules for doing so defined in CSS.
If the element does not represent an image, but the element already has intrinsic dimensions (e.g., from the dimension attributes or CSS rules), and either: the user agent has reason to believe that the image will become available and be rendered in due course, or the element has no alt attribute, or the Document is in quirks mode: The user agent is expected to treat the element as a replaced element whose content is the text that the element represents, if any, optionally alongside an icon indicating that the image is being obtained (if applicable). For input elements, the element is expected to appear button-like to indicate that the element is a button.
If the element is an img element that represents some text and the user agent does not expect this to change: The user agent is expected to treat the element as a non-replaced phrasing element whose content is the text, optionally with an icon indicating that an image is missing, so that the user can request the image be displayed or investigate why it is not rendering. In non-graphical contexts, such an icon should be omitted.
If the element is an img element that represents nothing and the user agent does not expect this to change: The user agent is expected to treat the element as an empty inline element. (In the absence of further styles, this will cause the element to essentially not be rendered.)
If the element is an input element that does not represent an image and the user agent does not expect this to change: The user agent is expected to treat the element as a replaced element consisting of a button whose content is the element’s alternative text. The intrinsic dimensions of the button are expected to be about one line in height and whatever width is necessary to render the text on one line.

The icons mentioned above are expected to be relatively small so as not to disrupt most text but be easily clickable. In a visual environment, for instance, icons could be 16 pixels by 16 pixels square, or 1em by 1em if the images are scalable. In an audio environment, the icon could be a short bleep. The icons are intended to indicate to the user that they can be used to get to whatever options the user agent provides for images.

All animated images with the same absolute URL and the same image data are expected to be rendered synchronized to the same timeline as a group, with the timeline starting at the time of the least recent addition to the group.

Note: In other words, when a second image with the same absolute URL and animated image data is inserted into a document, it jumps to the point in the animation cycle that is currently being displayed by the first image.

When a user agent is to restart the animation for an img element showing an animated image, all animated images with the same absolute URL and the same image data in that img element’s node document are expected to restart their animation from the beginning.

The following CSS rules are expected to apply when the Document is in quirks mode:

@namespace url(http://www.w3.org/1999/xhtml);

img[align=left i] { margin-right: 3px; }
img[align=right i] { margin-left: 3px; }

10.4.3. Attributes for embedded content and images

The following CSS rules are expected to apply as presentational hints:

@namespace url(http://www.w3.org/1999/xhtml);

iframe[frameborder=0], iframe[frameborder=no i] { border: none; }

applet[align=left i], embed[align=left i], iframe[align=left i],
img[align=left i], input[type=image i][align=left i], object[align=left i] {
  float: left;
}

applet[align=right i], embed[align=right i], iframe[align=right i],
img[align=right i], input[type=image i][align=right i], object[align=right i] {
  float: right;
}

applet[align=top i], embed[align=top i], iframe[align=top i],
img[align=top i], input[type=image i][align=top i], object[align=top i] {
  vertical-align: top;
}

applet[align=baseline i], embed[align=baseline i], iframe[align=baseline i],
img[align=baseline i], input[type=image i][align=baseline i], object[align=baseline i] {
  vertical-align: baseline;
}

applet[align=texttop i], embed[align=texttop i], iframe[align=texttop i],
img[align=texttop i], input[type=image i][align=texttop i], object[align=texttop i] {
  vertical-align: text-top;
}

applet[align=absmiddle i], embed[align=absmiddle i], iframe[align=absmiddle i],
img[align=absmiddle i], input[type=image i][align=absmiddle i], object[align=absmiddle i],
applet[align=abscenter i], embed[align=abscenter i], iframe[align=abscenter i],
img[align=abscenter i], input[type=image i][align=abscenter i], object[align=abscenter i] {
  vertical-align: middle;
}

applet[align=bottom i], embed[align=bottom i], iframe[align=bottom i],
img[align=bottom i], input[type=image i][align=bottom i],
object[align=bottom i] {
  vertical-align: bottom;
}

When an applet, embed, iframe, img, or object element, or an input element whose type attribute is in the Image Button state, has an align attribute whose value is an ASCII case-insensitive match for the string "center" or the string "middle", the user agent is expected to act as if the element’s vertical-align property was set to a value that aligns the vertical middle of the element with the parent element’s baseline.

The hspace attribute of applet, embed, iframe, img, or object elements, and input elements with a type attribute in the Image Button state, maps to the dimension properties margin-left and margin-right on the element.

The vspace attribute of applet, embed, iframe, img, or object elements, and input elements with a type attribute in the Image Button state, maps to the dimension properties margin-top and margin-bottom on the element.

When an img element, object element, or input element with a type attribute in the Image Button state has a border attribute whose value, when parsed using the rules for parsing non-negative integers, is found to be a number greater than zero, the user agent is expected to use the parsed value for eight presentational hints: four setting the parsed value as a pixel length for the element’s border-top-width, border-right-width, border-bottom-width, and border-left-width properties, and four setting the element’s border-top-style, border-right-style, border-bottom-style, and border-left-style properties to the value solid.

The width and height attributes on applet, embed, iframe, img, object or video elements, and input elements with a type attribute in the Image Button state and that either represents an image or that the user expects will eventually represent an image, map to the dimension properties width and height on the element respectively.

10.4.4. Image maps

Shapes on an image map are expected to act, for the purpose of the CSS cascade, as elements independent of the original area element that happen to match the same style rules but inherit from the img or object element.

For the purposes of the rendering, only the cursor property is expected to have any effect on the shape.

Thus, for example, if an area element has a style attribute that sets the cursor property to help, then when the user designates that shape, the cursor would change to a Help cursor.

Similarly, if an area element had a CSS rule that set its cursor property to inherit (or if no rule setting the cursor property matched the element at all), the shape’s cursor would be inherited from the img or object element of the image map, not from the parent of the area element.

10.5. Widgets

10.5.1. Introduction

Exactly how user agents render the elements in this section is not specified by this specification. User agents are encouraged to set the appearance CSS property appropriately to achieve platform-native appearances for widgets, and are expected to implement any relevant animations, etc, that are appropriate for the platform. [CSSUI]

10.5.2. The `button` element

The button element is expected to render as an inline-block box rendered as a button whose contents are the contents of the element.

10.5.3. The `details` and `summary` elements

details > summary:first-of-type {
  display: list-item;
  list-style: disclosure-closed inside;
}
details[open] > summary:first-of-type {
  list-style-type: disclosure-open;
}

The details element is expected to render as a block box. The element’s shadow tree is expected to take the element’s first child summary element, if any, and place it in a first block box container, and then take the element’s remaining descendants, if any, and place them in a second block box container.

The first container is expected to allow the user to request the details be shown or hidden.

The second container is expected to be removed from the rendering when the details element does not have an open attribute.

There are no specific rendering expecations for a summary element that is not the first child of its parent details element

The input element whose type attribute is in the Text, Search, Telephone, URL, or E-mail state, the element is expected to render as an inline-block box rendered as a text field. Additionally, the line-height property, if it has a computed value equivalent to a value that is less than 1.0, must have a used value of 1.0.

An input element whose type attribute is in the Password state, the element is expected to render as an inline-block box rendered as a text field whose contents are obscured.

If these text fields provide a text selection, then, when the user changes the current selection, the user agent is expected to queue a task to fire a simple event that bubbles named select at the element, using the user interaction task source as the task source.

If an input element whose type attribute is in one of the above states has a size attribute, and parsing that attribute’s value using the rules for parsing non-negative integers doesn’t generate an error, then the user agent is expected to use the attribute as a presentational hint for the width property on the element, with the value obtained from applying the converting a character width to pixels algorithm to the value of the attribute.

If an input element whose type attribute is in one of the above states does not have a size attribute, then the user agent is expected to act as if it had a user-agent-level style sheet rule setting the width property on the element to the value obtained from applying the converting a character width to pixels algorithm to the number 20.

The converting a character width to pixels algorithm returns (size-1)×avg + max, where size is the character width to convert, avg is the average character width of the primary font for the element for which the algorithm is being run, in pixels, and max is the maximum character width of that same font, also in pixels. (The element’s letter-spacing property does not affect the result.)

10.5.5. The `input` element as domain-specific widgets

An input element whose type attribute is in the Date state, the element is expected to render as an inline-block box depicting a Date control.

An input element whose type attribute is in the Month state, the element is expected to render as an inline-block box depicting a Month control.

An input element whose type attribute is in the Week state, the element is expected to render as an inline-block box depicting a Week control.

An input element whose type attribute is in the Time state, the element is expected to render as an inline-block box depicting a Time control.

An input element whose type attribute is in the Local Date and Time state, the element is expected to render as an inline-block box depicting a Local Date and Time control.

An input element whose type attribute is in the Number state, the element is expected to render as an inline-block box depicting a Number control.

These controls are all expected to be about one line high, and about as wide as necessary to show the widest possible value.

10.5.6. The `input` element as a range control

An input element whose type attribute is in the Range state, the element is expected to render as an inline-block box depicting a slider control.

When the control is wider than it is tall (or square), the control is expected to be a horizontal slider, with the lowest value on the right if the direction property on this element has a computed value of rtl, and on the left otherwise. When the control is taller than it is wide, it is expected to be a vertical slider, with the lowest value on the bottom.

Predefined suggested values (provided by the list attribute) are expected to be shown as tick marks on the slider, which the slider can snap to.

User agents are expected to use the used value of the direction property on the element to determine the direction in which the slider operates. Typically, a left-to-right (ltr) horizontal control would have the lowest value on the left and the highest value on the right, and vice versa.

10.5.7. The `input` element as a color well

An input element whose type attribute is in the Color state, the element is expected to render as an inline-block box depicting a color well, which, when activated, provides the user with a color picker (e.g., a color wheel or color palette) from which the color can be changed.

Predefined suggested values (provided by the list attribute) are expected to be shown in the color picker interface, not on the color well itself.

10.5.8. The `input` element as a checkbox and radio button widgets

An input element whose type attribute is in the Checkbox state, the element is expected to render as an inline-block box containing a single checkbox control, with no label.

An input element whose type attribute is in the Radio Button state, the element is expected to render as an inline-block box containing a single radio button control, with no label.

10.5.9. The `input` element as a file upload control

An input element whose type attribute is in the File Upload state, the element is expected to render as an inline-block box containing a span of text giving the file name(s) of the selected files, if any, followed by a button that, when activated, provides the user with a file picker from which the selection can be changed.

10.5.10. The `input` element as a button

An input element whose type attribute is in the Submit Button, Reset Button, or Button state, the element is expected to render as an inline-block box rendered as a button, about one line high, containing the contents of the element’s value attribute, if any, or text derived from the element’s type attribute in a user-agent-defined (and probably locale-specific) fashion, if not.

10.5.11. The `marquee` element

The marquee element, while the element is turned on, the element is expected to render in an animated fashion according to its attributes as follows:

If the element’s behavior attribute is in the scroll state

Slide the contents of the element in the direction described by the direction attribute as defined below, such that it begins off the start side of the marquee, and ends flush with the inner end side.

For example, if the direction attribute is left (the default), then the contents would start such that their left edge are off the side of the right edge of the marquee's content area, and the contents would then slide up to the point where the left edge of the contents are flush with the left inner edge of the marquee's content area.

Once the animation has ended, the user agent is expected to increment the marquee current loop index. If the element is still turned on after this, then the user agent is expected to restart the animation.

If the element’s behavior attribute is in the slide state

Slide the contents of the element in the direction described by the direction attribute as defined below, such that it begins off the start side of the marquee, and ends off the end side of the marquee.

For example, if the direction attribute is left (the default), then the contents would start such that their left edge are off the side of the right edge of the marquee's content area, and the contents would then slide up to the point where the right edge of the contents are flush with the left inner edge of the marquee's content area.

If the element’s behavior attribute is in the alternate state

When the marquee current loop index is even (or zero), slide the contents of the element in the direction described by the direction attribute as defined below, such that it begins flush with the start side of the marquee, and ends flush with the end side of the marquee.

When the marquee current loop index is odd, slide the contents of the element in the opposite direction than that described by the direction attribute as defined below, such that it begins flush with the end side of the marquee, and ends flush with the start side of the marquee.

For example, if the direction attribute is left (the default), then the contents would with their right edge flush with the right inner edge of the marquee's content area, and the contents would then slide up to the point where the left edge of the contents are flush with the left inner edge of the marquee's content area.

The direction attribute has the meanings described in the following table:

`direction` attribute state	Direction of animation	Start edge	End edge	Opposite direction
`left`	← Right to left	Right	Left	→ Left to Right
`right`	→ Left to Right	Left	Right	← Right to left
`up`	↑ Up (Bottom to Top)	Bottom	Top	↓ Down (Top to Bottom)
`down`	↓ Down (Top to Bottom)	Top	Bottom	↑ Up (Bottom to Top)

In any case, the animation should proceed such that there is a delay given by the marquee scroll interval between each frame, and such that the content moves at most the distance given by the marquee scroll distance with each frame.

When a marquee element has a bgcolor attribute set, the value is expected to be parsed using the rules for parsing a legacy color value, and if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the element’s background-color property to the resulting color.

The width and height attributes on a marquee element map to the dimension properties width and height on the element respectively.

The intrinsic height of a marquee element with its direction attribute in the up or down states is 200 CSS pixels.

The vspace attribute of a marquee element maps to the dimension properties margin-top and margin-bottom on the element. The hspace attribute of a marquee element maps to the dimension properties margin-left and margin-right on the element.

The overflow property on the marquee element is expected to be ignored; overflow is expected to always be hidden.

10.5.12. The `meter` element

The meter element is expected to render as an inline-block box with a height of "1em" and a width of "5em", a vertical-align of "-0.2em", and with its contents depicting a gauge.

When the element is wider than it is tall (or square), the depiction is expected to be of a horizontal gauge, with the minimum value on the right if the direction property on this element has a computed value of rtl, and on the left otherwise. When the element is taller than it is wide, it is expected to depict a vertical gauge, with the minimum value on the bottom.

User agents are expected to use a presentation consistent with platform conventions for gauges, if any.

Note: Requirements for what must be depicted in the gauge are included in the definition of the meter element.

10.5.13. The `progress` element

The progress element is expected to render as an inline-block box with a height of "1em" and a width of "10em", and a vertical-align of "-0.2em".

When the element is wider than it is tall, the element is expected to be depicted as a horizontal progress bar, with the start on the right and the end on the left if the direction property on this element has a computed value of rtl, and with the start on the left and the end on the right otherwise. When the element is taller than it is wide, it is expected to be depicted as a vertical progress bar, with the lowest value on the bottom. When the element is square, it is expected to be depicted as a direction-independent progress widget (e.g., a circular progress ring).

User agents are expected to use a presentation consistent with platform conventions for progress bars. In particular, user agents are expected to use different presentations for determinate and indeterminate progress bars. User agents are also expected to vary the presentation based on the dimensions of the element.

For example, on some platforms for showing indeterminate progress there is a "spinner" progress indicator with square dimensions, which could be used when the element is square, and an indeterminate progress bar, which could be used when the element is wide.

Note: Requirements for how to determine if the progress bar is determinate or indeterminate, and what progress a determinate progress bar is to show, are included in the definition of the progress element.

10.5.14. The `select` element

A select element whose multiple attribute is present, the element is expected to render as a multi-select list box.

A select element whose multiple attribute is absent, and the element’s display size is greater than 1, the element is expected to render as a single-select list box.

When the element renders as a list box, it is expected to render as an inline-block box whose height is the height necessary to contain as many rows for items as given by the element’s display size, or four rows if the attribute is absent, and whose width is the width of the select’s labels plus the width of a scrollbar.

A select element whose multiple attribute is absent, and the element’s display size is 1, the element is expected to render as a one-line drop down box whose width is the width of the select’s labels.

In either case (list box or drop-down box), the element’s items are expected to be the element’s list of options, with the element’s optgroup element children providing headers for groups of options where applicable.

An optgroup element is expected to be rendered by displaying the element’s label attribute.

An option element is expected to be rendered by displaying the element’s label, indented under its optgroup element if it has one.

The width of the select’s labels is the wider of the width necessary to render the widest optgroup, and the width necessary to render the widest option element in the element’s list of options (including its indent, if any).

If a select element contains a placeholder label option, the user agent is expected to render that option in a manner that conveys that it is a label, rather than a valid option of the control. This can include preventing the placeholder label option from being explicitly selected by the user. When the placeholder label option's selectedness is true, the control is expected to be displayed in a fashion that indicates that no valid option is currently selected.

User agents are expected to render the labels in a select in such a manner that any alignment remains consistent whether the label is being displayed as part of the page.

10.5.15. The `textarea` element

@namespace url(http://www.w3.org/1999/xhtml);

textarea { white-space: pre-wrap; }

The textarea element is expected to render as an inline-block box rendered as a multiline text field. If this text field provides a selection, the user agent is expected to queue a task to fire a simple event that bubbles named select at the element, using the user interaction task source as the task source.

If the element has a cols attribute, and parsing that attribute’s value using the rules for parsing non-negative integers doesn’t generate an error, then the user agent is expected to use the attribute as a presentational hint for the width property on the element, with the value being the textarea effective width (as defined below). Otherwise, the user agent is expected to act as if it had a user-agent-level style sheet rule setting the width property on the element to the textarea effective width.

The textarea effective width of a textarea element is size×avg + sbw, where size is the element’s character width, avg is the average character width of the primary font of the element, in CSS pixels, and sbw is the width of a scroll bar, in CSS pixels. (The element’s letter-spacing property does not affect the result.)

If the element has a rows attribute, and parsing that attribute’s value using the rules for parsing non-negative integers doesn’t generate an error, then the user agent is expected to use the attribute as a presentational hint for the height property on the element, with the value being the textarea effective height (as defined below). Otherwise, the user agent is expected to act as if it had a user-agent-level style sheet rule setting the height property on the element to the textarea effective height.

The textarea effective height of a textarea element is the height in CSS pixels of the number of lines specified the element’s character height, plus the height of a scrollbar in CSS pixels.

User agents are expected to apply the white-space CSS property to textarea elements. For historical reasons, if the element has a wrap attribute whose value is an ASCII case-insensitive match for the string "off", then the user agent is expected to treat the attribute as a presentational hint setting the element’s white-space property to pre.

10.6. Frames and framesets

User agent are expected to render frameset elements as a box with the height and width of the viewport, with a surface rendered according to the following layout algorithm:

The cols and rows variables are lists of zero or more pairs consisting of a number and a unit, the unit being one of percentage, relative, and absolute.

Use the rules for parsing a list of dimensions to parse the value of the element’s cols attribute, if there is one. Let cols be the result, or an empty list if there is no such attribute.

Use the rules for parsing a list of dimensions to parse the value of the element’s rows attribute, if there is one. Let rows be the result, or an empty list if there is no such attribute.
For any of the entries in cols or rows that have the number zero and the unit relative, change the entry’s number to one.
If cols has no entries, then add a single entry consisting of the value 1 and the unit relative to cols.

If rows has no entries, then add a single entry consisting of the value 1 and the unit relative to rows.
Invoke the algorithm defined below to convert a list of dimensions to a list of pixel values using cols as the input list, and the width of the surface that the frameset is being rendered into, in CSS pixels, as the input dimension. Let sized cols be the resulting list.

Invoke the algorithm defined below to convert a list of dimensions to a list of pixel values using rows as the input list, and the height of the surface that the frameset is being rendered into, in CSS pixels, as the input dimension. Let sized rows be the resulting list.
Split the surface into a grid of w×h rectangles, where w is the number of entries in sized cols and h is the number of entries in sized rows.

Size the columns so that each column in the grid is as many CSS pixels wide as the corresponding entry in the sized cols list.

Size the rows so that each row in the grid is as many CSS pixels high as the corresponding entry in the sized rows list.
Let children be the list of frame and frameset elements that are children of the frameset element for which the algorithm was invoked.
For each row of the grid of rectangles created in the previous step, from top to bottom, run these substeps:
1. For each rectangle in the row, from left to right, run these substeps:
  1. If there are any elements left in children, take the first element in the list, and assign it to the rectangle.
    
    If this is a frameset element, then recurse the entire frameset layout algorithm for that frameset element, with the rectangle as the surface.
    
    Otherwise, it is a frame element; render its nested browsing context, positioned and sized to fit the rectangle.
  2. If there are any elements left in children, remove the first element from children.
If the frameset element has a border, draw an outer set of borders around the rectangles, using the element’s frame border color.

For each rectangle, if there is an element assigned to that rectangle, and that element has a border, draw an inner set of borders around that rectangle, using the element’s frame border color.

For each (visible) border that does not abut a rectangle that is assigned a frame element with a noresize attribute (including rectangles in further nested frameset elements), the user agent is expected to allow the user to move the border, resizing the rectangles within, keeping the proportions of any nested frameset grids.

A frameset or frame element has a border if the following algorithm returns true:
1. If the element has a frameborder attribute whose value is not the empty string and whose first character is either a U+0031 DIGIT ONE (1) character, a U+0079 LATIN SMALL LETTER Y character (y), or a U+0059 LATIN CAPITAL LETTER Y character (Y), then return true.
2. Otherwise, if the element has a frameborder attribute, return false.
3. Otherwise, if the element has a parent element that is a frameset element, then return true if that element has a border, and false if it does not.
4. Otherwise, return true.
The frame border color of a frameset or frame element is the color obtained from the following algorithm:
1. If the element has a bordercolor attribute, and applying the rules for parsing a legacy color value to that attribute’s value does not result in an error, then return the color so obtained.
2. Otherwise, if the element has a parent element that is a frameset element, then return the frame border color of that element.
3. Otherwise, return gray.

The algorithm to convert a list of dimensions to a list of pixel values consists of the following steps:

Let input list be the list of numbers and units passed to the algorithm.

Let output list be a list of numbers the same length as input list, all zero.

Entries in output list correspond to the entries in input list that have the same position.
Let input dimension be the size passed to the algorithm.
Let count percentage be the number of entries in input list whose unit is percentage.

Let total percentage be the sum of all the numbers in input list whose unit is percentage.

Let count relative be the number of entries in input list whose unit is relative.

Let total relative be the sum of all the numbers in input list whose unit is relative.

Let count absolute be the number of entries in input list whose unit is absolute.

Let total absolute be the sum of all the numbers in input list whose unit is absolute.

Let remaining space be the value of input dimension.
If total absolute is greater than remaining space, then for each entry in input list whose unit is absolute, set the corresponding value in output list to the number of the entry in input list multiplied by remaining space and divided by total absolute. Then, set remaining space to zero.

Otherwise, for each entry in input list whose unit is absolute, set the corresponding value in output list to the number of the entry in input list. Then, decrement remaining space by total absolute.
If total percentage multiplied by the input dimension and divided by 100 is greater than remaining space, then for each entry in input list whose unit is percentage, set the corresponding value in output list to the number of the entry in input list multiplied by remaining space and divided by total percentage. Then, set remaining space to zero.

Otherwise, for each entry in input list whose unit is percentage, set the corresponding value in output list to the number of the entry in input list multiplied by the input dimension and divided by 100. Then, decrement remaining space by total percentage multiplied by the input dimension and divided by 100.
For each entry in input list whose unit is relative, set the corresponding value in output list to the number of the entry in input list multiplied by remaining space and divided by total relative.
Return output list.

User agents working with integer values for frame widths (as opposed to user agents that can lay frames out with subpixel accuracy) are expected to distribute the remainder first to the last entry whose unit is relative, then equally (not proportionally) to each entry whose unit is percentage, then equally (not proportionally) to each entry whose unit is absolute, and finally, failing all else, to the last entry.

The contents of a frame element that does not have a frameset parent are expected to be rendered as transparent black; the user agent is expected to not render the nested browsing context in this case, and that nested browsing context is expected to have a viewport with zero width and zero height.

10.7. Interactive media

User agents are expected to allow the user to control aspects of hyperlink activation and §4.10.21 Form submission, such as which browsing context is to be used for the subsequent navigation.

User agents are expected to allow users to discover the destination of hyperlinks and of forms before triggering their navigation.

User agents may allow users to navigate browsing contexts to the URLs indicated by the cite attributes on q, blockquote, ins, and del elements.

User agents may surface hyperlinks created by link elements in their user interface.

Note: While link elements that create hyperlinks will match the :link or :visited pseudo-classes, will react to clicks if visible, and so forth, this does not extend to any browser interface constructs that expose those same links. Activating a link through the browser’s interface, rather than in the page itself, does not trigger click events and the like.

10.7.2. The `title` attribute

User agents are expected to expose the advisory information of elements upon user request, and to make the user aware of the presence of such information.

On interactive graphical systems where the user can use a pointing device, this could take the form of a tooltip. When the user is unable to use a pointing device, then the user agent is expected to make the content available in some other fashion, e.g., by making the element a focusable area and always displaying the advisory information of the currently focused element.

U+000A LINE FEED (LF) characters are expected to cause line breaks in the tooltip; U+0009 CHARACTER TABULATION (tab) characters are expected to render as a non-zero horizontal shift that lines up the next glyph with the next tab stop, with tab stops occurring at points that are multiples of 8 times the width of a U+0020 SPACE character.

For example, a visual user agent could make elements with a title attribute focusable, and could make any focused element with a title attribute show its tooltip under the element while the element has focus. This would allow a user to tab around the document to find all the advisory text.

As another example, a screen reader could provide an audio cue when reading an element with a tooltip, with an associated key to read the last tooltip for which a cue was played.

10.7.3. Editing hosts

The current text editing caret (i.e., the active range, if it is empty and in an editing host), if any, is expected to act like an inline replaced element with the vertical dimensions of the caret and with zero width for the purposes of the CSS rendering model.

Note: This means that even an empty block can have the caret inside it, and that when the caret is in such an element, it prevents margins from collapsing through the element.

10.7.4. Text rendered in native user interfaces

User agents are expected to honor the Unicode semantics of text that is exposed in user interfaces, for example supporting the bidirectional algorithm in text shown in dialogs, title bars, and tooltips. Text from the contents of elements is expected to be rendered in a manner that honors the directionality of the element from which the text was obtained. Text from attributes is expected to be rendered in a manner that honours the directionality of the attribute.

Consider the following markup, which has Hebrew text asking for a programming language, the languages being text for which a left-to-right direction is important given the punctuation in some of their names:

<p dir="rtl" lang="he">
  <label>
    בחר שפת תכנות:
    <select>
      <option dir="ltr">C++</option>
      <option dir="ltr">C#</option>
      <option dir="ltr">FreePascal</option>
      <option dir="ltr">F#</option>
    </select>
  </label>
</p>

If the select element was rendered as a drop down box, a correct rendering would ensure that the punctuation was the same both in the drop down, and in the box showing the current selection.

The directionality of attributes depends on the attribute and on the element’s dir attribute, as the following example demonstrates. Consider this markup:

<table>
  <tr>
    <th abbr="(א" dir="ltr">A</th>
    <th abbr="(א" dir="rtl">A</th>
    <th abbr="(א" dir="auto">A</th>
  </tr>
</table>

If the abbr attributes are rendered, e.g., in a tooltip or other user interface, the first will have a left parenthesis (because the direction is ltr), the second will have a right parenthesis (because the direction is rtl), and the third will have a right parenthesis (because the direction is determined from the attribute value to be rtl).

However, if instead the attribute was not a directionality-capable attribute, the results would be different:

<table>
  <tr>
    <th>A
    <th>A
    <th>A
</table>

In this case, if the user agent were to expose the data-abbr attribute in the user interface (e.g., in a debugging environment), the last case would be rendered with a left parenthesis, because the direction would be determined from the element’s contents.

A string provided by a script (e.g., the argument to window.alert()) is expected to be treated as an independent set of one or more bidirectional algorithm paragraphs when displayed, as defined by the bidirectional algorithm, including, for instance, supporting the paragraph-breaking behavior of U+000A LINE FEED (LF) characters. For the purposes of determining the paragraph level of such text in the bidirectional algorithm, this specification does not provide a higher-level override of rules P2 and P3. [BIDI]

When necessary, authors can enforce a particular direction for a given paragraph by starting it with the Unicode U+200E LEFT-TO-RIGHT MARK or U+200F RIGHT-TO-LEFT MARK characters.

Thus, the following script:

alert('\u05DC\u05DE\u05D3 HTML \u05D4\u05D9\u05D5\u05DD!')

...would always result in a message reading "למד LMTH היום!" (not "דמל HTML םויה!"), regardless of the language of the user agent interface or the direction of the page or any of its elements.

For a more complex example, consider the following script:

/* Warning: this script does not handle right-to-left scripts correctly */
var s;
if (s = prompt('What is your name?')) {
  alert(s + '! Ok, Fred, ' + s + ', and Wilma will get the car.');
}

When the user enters "Kitty", the user agent would alert "Kitty! Ok, Fred, Kitty, and Wilma will get the car.". However, if the user enters "لا أفهم", then the bidirectional algorithm will determine that the direction of the paragraph is right-to-left, and so the output will be the following unintended mess: "لا أفهم! derF ,kO, لا أفهم, rac eht teg lliw amliW dna."

To force an alert that starts with user-provided text (or other text of unknown directionality) to render left-to-right, the string can be prefixed with a U+200E LEFT-TO-RIGHT MARK character:

var s;
if (s = prompt('What is your name?')) {
  alert('\u200E' + s + '! Ok, Fred, ' + s + ', and Wilma will get the car.');
}

10.8. Print media

User agents are expected to allow the user to request the opportunity to obtain a physical form (or a representation of a physical form) of a Document. For example, selecting the option to print a page or convert it to PDF format. [PDF]

When the user actually obtains a physical form (or a representation of a physical form) of a Document, the user agent is expected to create a new rendering of the Document for the print media.

10.9. Unstyled XML documents

HTML user agents may, in certain circumstances, find themselves rendering non-HTML documents that use vocabularies for which they lack any built-in knowledge. This section provides for a way for user agents to handle such documents in a somewhat useful manner.

While a Document is an unstyled document, the user agent is expected to render an unstyled document view.

A Document is an unstyled document while it matches the following conditions:

The Document has no author style sheets (whether referenced by HTTP headers, processing instructions, elements like link, inline elements like style, or any other mechanism).
None of the elements in the Document have any presentational hints.
None of the elements in the Document have any style attributes.
None of the elements in the Document are in any of the following namespaces: HTML namespace, SVG namespace, MathML namespace
The Document has no focusable area (e.g., from XLink) other than the viewport.
The Document has no hyperlinks (e.g., from XLink).
There exists no script whose settings object specifies this Document as the responsible document.
None of the elements in the Document have any registered event listeners.

An unstyled document view is one where the DOM is not rendered according to CSS (which would, since there are no applicable styles in this context, just result in a wall of text), but is instead rendered in a manner that is useful for a developer. This could consist of just showing the Document object’s source, maybe with syntax highlighting, or it could consist of displaying just the DOM tree, or simply a message saying that the page is not a styled document.

Note: If a Document stops being an unstyled document, then the conditions above stop applying, and thus a user agent following these requirements will switch to using the regular CSS rendering.

10. Rendering

10.1. Introduction

10.2. The CSS user agent style sheet and presentational hints

10.3. Non-replaced elements

10.3.1. Hidden elements

10.3.2. The page

10.3.3. Flow content

10.3.4. Phrasing content

10.3.5. Bidirectional text

10.3.6. Quotes

10.3.6.1. Multilingual documents

10.3.7. Sections and headings

10.3.8. Lists

10.3.9. Tables

10.3.10. Margin collapsing quirks

10.3.11. Form controls

10.3.12. The hr element

10.3.13. The fieldset and legend elements

10.4. Replaced elements

10.4.1. Embedded content

10.4.2. Images

10.4.3. Attributes for embedded content and images

10.4.4. Image maps

10.5. Widgets

10.5.1. Introduction

10.5.2. The button element

10.5.3. The details and summary elements

10.5.4. The input element as a text entry widget.

10.5.5. The input element as domain-specific widgets

10.5.6. The input element as a range control

10.5.7. The input element as a color well

10.5.8. The input element as a checkbox and radio button widgets

10.5.9. The input element as a file upload control

10.5.10. The input element as a button

10.5.11. The marquee element

10.5.12. The meter element

10.5.13. The progress element

10.5.14. The select element

10.5.15. The textarea element

10.6. Frames and framesets

10.7. Interactive media

10.7.1. Links, forms, and navigation

10.7.2. The title attribute

10.7.3. Editing hosts

10.7.4. Text rendered in native user interfaces

10.8. Print media

10.9. Unstyled XML documents

10.3.12. The `hr` element

10.3.13. The `fieldset` and `legend` elements

10.5.2. The `button` element

10.5.3. The `details` and `summary` elements

10.5.4. The `input` element as a text entry widget.

10.5.5. The `input` element as domain-specific widgets

10.5.6. The `input` element as a range control

10.5.7. The `input` element as a color well

10.5.8. The `input` element as a checkbox and radio button widgets

10.5.9. The `input` element as a file upload control

10.5.10. The `input` element as a button

10.5.11. The `marquee` element

10.5.12. The `meter` element

10.5.13. The `progress` element

10.5.14. The `select` element

10.5.15. The `textarea` element

10.7.2. The `title` attribute