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<!doctype html><html lang="en"> <head> <meta content="text/html; charset=utf-8" http-equiv="Content-Type"> <meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name="viewport"> <title>CSS Mobile Profile 2.0</title> <meta content="ED" name="w3c-status"> <link href="https://www.w3.org/StyleSheets/TR/2021/W3C-ED" rel="stylesheet"> <meta content="Bikeshed version 742f3d674, updated Mon Nov 4 14:56:54 2024 -0800" name="generator"> <link href="https://www.w3.org/TR/css-mobile/" rel="canonical"> <link href="https://drafts.csswg.org/csslogo.ico" rel="icon"> <meta content="29252b2aba280f88362361e65ae420776a149c6d" name="revision"> <meta content="dark light" name="color-scheme"> <link href="https://www.w3.org/StyleSheets/TR/2021/dark.css" media="(prefers-color-scheme: dark)" rel="stylesheet" type="text/css"> <style type="text/css"> table.features th { background: #00589f; color: #fff; text-align: left; padding: 0.2em 0.2em 0.2em 0.5em; } table.features td { vertical-align: top; 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} [data-link-type="property"]::after, [data-link-type="propdesc"]::after, [data-link-type="descriptor"]::after, [data-link-type="value"]::after, [data-link-type="function"]::after, [data-link-type="at-rule"]::after, [data-link-type="selector"]::after, [data-link-type="maybe"]::after { content: "’"; } [data-link-type].production::before, [data-link-type].production::after, .prod [data-link-type]::before, .prod [data-link-type]::after { content: ""; } [data-link-type=element], [data-link-type=element-attr] { font-family: Menlo, Consolas, "DejaVu Sans Mono", monospace; font-size: .9em; } [data-link-type=element]::before { content: "<" } [data-link-type=element]::after { content: ">" } [data-link-type=biblio] { white-space: pre; } @media (prefers-color-scheme: dark) { :root { --selflink-text: black; --selflink-bg: silver; --selflink-hover-text: white; } } </style> <style>/* Boilerplate: style-colors */ /* Any --*-text not paired with a --*-bg is assumed to have a transparent bg */ :root { color-scheme: light dark; 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--indextable-hover-text: black; --indextable-hover-bg: #f7f8f9; --outdatedspec-bg: rgba(0, 0, 0, .5); --outdatedspec-text: black; --outdated-bg: maroon; --outdated-text: white; --outdated-shadow: red; --editedrec-bg: darkorange; } @media (prefers-color-scheme: dark) { :root { --text: #ddd; --bg: black; --unofficial-watermark: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='400' height='400'%3E%3Cg fill='%23100808' transform='translate(200 200) rotate(-45) translate(-200 -200)' stroke='%23100808' stroke-width='3'%3E%3Ctext x='50%25' y='220' style='font: bold 70px sans-serif; text-anchor: middle; letter-spacing: 6px;'%3EUNOFFICIAL%3C/text%3E%3Ctext x='50%25' y='305' style='font: bold 70px sans-serif; text-anchor: middle; letter-spacing: 6px;'%3EDRAFT%3C/text%3E%3C/g%3E%3C/svg%3E"); --logo-bg: #1a5e9a; --logo-active-bg: #c00; --logo-text: white; --tocnav-normal-text: #999; --tocnav-normal-bg: var(--bg); --tocnav-hover-text: var(--tocnav-normal-text); --tocnav-hover-bg: #080808; 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--example-border: hsl(50deg, 90%, 60%); --example-bg: var(--borderedblock-bg); --example-text: var(--text); --exampleheading-text: hsl(50deg, 70%, 70%); --note-border: hsl(120deg, 100%, 35%); --note-bg: var(--borderedblock-bg); --note-text: var(--text); --noteheading-text: hsl(120, 70%, 70%); --notesummary-underline: silver; --assertion-border: #444; --assertion-bg: var(--borderedblock-bg); --assertion-text: var(--text); --advisement-border: orange; --advisement-bg: #222218; --advisement-text: var(--text); --advisementheading-text: #f84; --warning-border: red; --warning-bg: hsla(40,100%,20%,0.95); --warning-text: var(--text); --amendment-border: #330099; --amendment-bg: #080010; --amendment-text: var(--text); --amendmentheading-text: #cc00ff; --def-border: #8ccbf2; --def-bg: #080818; --def-text: var(--text); --defrow-border: #136; --datacell-border: silver; --indexinfo-text: #aaa; --indextable-hover-text: var(--text); --indextable-hover-bg: #181818; --outdatedspec-bg: rgba(255, 255, 255, .5); --outdatedspec-text: black; --outdated-bg: maroon; --outdated-text: white; --outdated-shadow: red; --editedrec-bg: darkorange; } /* In case a transparent-bg image doesn't expect to be on a dark bg, which is quite common in practice... */ img { background: white; } } </style> <style>/* Boilerplate: style-counters */ body { counter-reset: example figure issue; } .issue { counter-increment: issue; } .issue:not(.no-marker)::before { content: "Issue " counter(issue); } .example { counter-increment: example; } .example:not(.no-marker)::before { content: "Example " counter(example); } .invalid.example:not(.no-marker)::before, .illegal.example:not(.no-marker)::before { content: "Invalid Example" counter(example); } figcaption { counter-increment: figure; } figcaption:not(.no-marker)::before { content: "Figure " counter(figure) " "; } </style> <style>/* Boilerplate: style-issues */ a[href].issue-return { float: right; float: inline-end; color: var(--issueheading-text); font-weight: bold; text-decoration: none; } </style> <style>/* Boilerplate: style-md-lists */ /* This is a weird hack for me not yet following the commonmark spec regarding paragraph and lists. */ [data-md] > :first-child { margin-top: 0; } [data-md] > :last-child { margin-bottom: 0; } </style> <style>/* Boilerplate: style-selflinks */ :root { --selflink-text: white; --selflink-bg: gray; --selflink-hover-text: black; } .heading, .issue, .note, .example, li, dt { position: relative; } a.self-link { position: absolute; top: 0; left: calc(-1 * (3.5rem - 26px)); width: calc(3.5rem - 26px); height: 2em; text-align: center; border: none; transition: opacity .2s; opacity: .5; } a.self-link:hover { opacity: 1; } .heading > a.self-link { font-size: 83%; } .example > a.self-link, .note > a.self-link, .issue > a.self-link { /* These blocks are overflow:auto, so positioning outside doesn't work. */ left: auto; right: 0; } li > a.self-link { left: calc(-1 * (3.5rem - 26px) - 2em); } dfn > a.self-link { top: auto; left: auto; opacity: 0; width: 1.5em; height: 1.5em; background: var(--selflink-bg); color: var(--selflink-text); font-style: normal; transition: opacity .2s, background-color .2s, color .2s; } dfn:hover > a.self-link { opacity: 1; } dfn > a.self-link:hover { color: var(--selflink-hover-text); } a.self-link::before { content: "¶"; } .heading > a.self-link::before { content: "§"; } dfn > a.self-link::before { content: "#"; } </style> <style>/* Boilerplate: style-wpt */ :root { --wpt-border: hsl(0, 0%, 60%); --wpt-bg: hsl(0, 0%, 95%); --wpt-text: var(--text); --wptheading-text: hsl(0, 0%, 30%); } @media (prefers-color-scheme: dark) { :root { --wpt-border: hsl(0, 0%, 30%); --wpt-bg: var(--borderedblock-bg); --wpt-text: var(--text); --wptheading-text: hsl(0, 0%, 60%); } } .wpt-tests-block { list-style: none; border-left: .5em solid var(--wpt-border); background: var(--wpt-bg); color: var(--wpt-text); margin: 1em auto; padding: .5em; } .wpt-tests-block summary { color: var(--wptheading-text); font-weight: normal; text-transform: uppercase; } .wpt-tests-block summary::marker{ color: var(--wpt-border); } .wpt-tests-block summary:hover::marker{ color: var(--wpt-text); } /* The only content of a wpt test block in its closed state is the <summary>, which contains the word TESTS, and that is absolutely positioned. In that closed state, wpt test blocks are styled to have a top margin whose height is exactly equal to the height of the absolutely positioned <summary>, and no other background/padding/margin/border. The wpt test block elements will therefore allow the maring of the previous/next block elements to collapse through them; if this combined margin would be larger than its own top margin, it stays as is, and therefore the pre-existing vertical rhythm of the document is undisturbed. If that combined margin would be smaller, it is grown to that size. This means that the wpt test block ensures that there's always enough vertical space to insert the summary, without adding more than is needed. */ .wpt-tests-block:not([open]){ padding: 0; border: none; background: none; font-size: 0.75em; line-height: 1; position: relative; margin: 1em 0 0; } .wpt-tests-block:not([open]) summary { position: absolute; right: 0; bottom: 0; } /* It is possible that both the last child of a block element and the block element itself would be annotated with a <wpt> block each. If the block element has a padding or a border, that's fine, but otherwise the bottom margin of the block and of its last child would collapse and both <wpt> elements would overlap, being both placed there. To avoid that, add 1px of padding to the <wpt> element annotating the last child to prevent the bottom margin of the block and of its last child from collapsing (and as much negative margin, as wel only want to prevent margin collapsing, but are not trying to actually take more space). */ .wpt-tests-block:not([open]):last-child { padding-bottom: 1px; margin-bottom: -1px; } /* Exception to the previous rule: don't do that in non-last list items, because it's not necessary, and would therefore consume more space than strictly needed. Lists must have list items as children, not <wpt> elements, so a <wpt> element cannot be a sibling of a list item, and the collision that the previous rule avoids cannot happen. */ li:not(:last-child) > .wpt-tests-block:not([open]):last-child, dd:not(:last-child) > .wpt-tests-block:not([open]):last-child { padding-bottom: 0; margin-bottom: 0; } .wpt-tests-block:not([open]):not(:hover){ opacity: 0.5; } .wpt-tests-list { list-style: none; display: grid; margin: 0; padding: 0; grid-template-columns: 1fr max-content auto auto; grid-column-gap: .5em; } .wpt-tests-block hr:last-child { display: none; } .wpt-test { display: contents; } .wpt-test > a { text-decoration: underline; border: none; } .wpt-test > .wpt-name { grid-column: 1; } .wpt-test > .wpt-results { grid-column: 2; } .wpt-test > .wpt-live { grid-column: 3; } .wpt-test > .wpt-source { grid-column: 4; } .wpt-test > .wpt-results { display: flex; gap: .1em; } .wpt-test .wpt-result { display: inline-block; height: 1em; width: 1em; border-radius: 50%; position: relative; } </style> <body class="h-entry"> <div class="head"> <p data-fill-with="logo"><a class="logo" href="https://www.w3.org/"> <img alt="W3C" height="48" src="https://www.w3.org/StyleSheets/TR/2021/logos/W3C" width="72"> </a> </p> <h1 class="p-name no-ref" id="title">CSS Mobile Profile 2.0</h1> <p id="w3c-state"><a href="https://www.w3.org/standards/types/#ED">Editor’s Draft</a>, <time class="dt-updated" datetime="2021-11-15">15 November 2021</time></p> <details open> <summary>More details about this document</summary> <div data-fill-with="spec-metadata"> <dl> <dt>This version: <dd><a class="u-url" href="https://drafts.csswg.org/css-mobile/">https://drafts.csswg.org/css-mobile/</a> <dt>Latest published version: <dd><a href="https://www.w3.org/TR/css-mobile/">https://www.w3.org/TR/css-mobile/</a> <dt>Previous Versions: <dd><a href="https://www.w3.org/TR/2014/NOTE-css-mobile-20141014/" rel="prev">https://www.w3.org/TR/2014/NOTE-css-mobile-20141014/</a> <dt>Feedback: <dd><a href="https://github.com/w3c/csswg-drafts/labels/css-mobile">CSSWG Issues Repository</a> <dt class="editor">Editor: <dd class="editor p-author h-card vcard" data-editor-id="3343"><a class="p-name fn u-email email" href="mailto:bert@w3.org">Bert Bos</a> (<span class="p-org org">W3C</span>) <dt>Suggest an Edit for this Spec: <dd><a href="https://github.com/w3c/csswg-drafts/blob/main/css-mobile/Overview.bs">GitHub Editor</a> <dt>Previous editors: <dd>Svante Schubert, Sun Microsystems Inc. <dd>Robin Berjon, Expway </dl> </div> </details> <div data-fill-with="warning"></div> <p class="copyright" data-fill-with="copyright"><a href="https://www.w3.org/policies/#copyright">Copyright</a> © 2021 <a href="https://www.w3.org/">World Wide Web Consortium</a>. <abbr title="World Wide Web Consortium">W3C</abbr><sup>®</sup> <a href="https://www.w3.org/policies/#Legal_Disclaimer">liability</a>, <a href="https://www.w3.org/policies/#W3C_Trademarks">trademark</a> and <a href="https://www.w3.org/copyright/software-license/" rel="license" title="W3C Software and Document License">permissive document license</a> rules apply. </p> <hr title="Separator for header"> </div> <div class="p-summary" data-fill-with="abstract"> <h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2> <p>This specification defines in general a subset of <abbr title="Cascading Style Sheets">CSS</abbr> 2.1 <a data-link-type="biblio" href="#biblio-css21" title="Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification">[CSS21]</a> that is to be considered a baseline for interoperability between implementations of <abbr title="Cascading Style Sheets">CSS</abbr> on constrained devices (e.g. mobile phones). Its intent is <em>not</em> to produce a profile of <abbr title="Cascading Style Sheets">CSS</abbr> incompatible with the complete specification, but rather to ensure that implementations that due to platform limitations cannot support the entire specification implement a common subset that is interoperable not only amongst constrained implementations but also with complete ones. Additionally, this specification aligns itself as much as possible with the <abbr title="Open Mobile Alliance">OMA</abbr> Wireless <abbr title="Cascading Style Sheets">CSS</abbr> 1.1 <a data-link-type="biblio" href="#biblio-wcss11" title="Wireless CSS Specification.">[WCSS11]</a> specification. At the same time, <abbr title="Open Mobile Alliance">OMA</abbr> is doing alignment work in <abbr title="Open Mobile Alliance">OMA</abbr> Wireless <abbr title="Cascading Style Sheets">CSS</abbr> 1.2 <a data-link-type="biblio" href="#biblio-wcss12" title="Wireless CSS Specification Version 1.2.">[WCSS12]</a>. It is aimed at aligning the mandatory compliance items between <abbr title="Cascading Style Sheets">CSS</abbr> Mobile Profile 2.0 and <abbr title="Open Mobile Alliance">OMA</abbr> Wireless <abbr title="Cascading Style Sheets">CSS</abbr> 1.2 <span title="Wireless CSS Specification Version 1.2.">[WCSS12]</span>.</p> <p class="mtb"><strong>This profile is obsolete. Please see the latest <a href="https://www.w3.org/TR/CSS/">CSS Snapshot</a> for the specifications that make up CSS.</strong></p> <a href="https://www.w3.org/TR/CSS/">CSS</a> is a language for describing the rendering of structured documents (such as HTML and XML) on screen, on paper, etc. <script> const githubPrefix = "https://w3c.github.io/csswg-drafts/"; if(location.href.slice(0, githubPrefix.length) == githubPrefix) { const suffix = location.href.slice(githubPrefix.length); const draftUrl = "https://drafts.csswg.org/" + suffix; window.location.replace(draftUrl); } </script> </div> <h2 class="no-num no-toc no-ref heading settled" id="sotd"><span class="content">Status of this document</span></h2> <div data-fill-with="status"> <p> This is a public copy of the editors’ draft. It is provided for discussion only and may change at any moment. Its publication here does not imply endorsement of its contents by W3C. Don’t cite this document other than as work in progress. </p> <p>Please send feedback by <a href="https://github.com/w3c/csswg-drafts/issues">filing issues in GitHub</a> (preferred), including the spec code “css-mobile” in the title, like this: “[css-mobile] <i>…summary of comment…</i>”. All issues and comments are <a href="https://lists.w3.org/Archives/Public/public-css-archive/">archived</a>. Alternately, feedback can be sent to the (<a href="https://lists.w3.org/Archives/Public/www-style/">archived</a>) public mailing list <a href="mailto:www-style@w3.org?Subject=%5Bcss-mobile%5D%20PUT%20SUBJECT%20HERE">www-style@w3.org</a>. </p> <p>This document is governed by the <a href="https://www.w3.org/policies/process/20231103/" id="w3c_process_revision">03 November 2023 W3C Process Document</a>. </p> <p></p> <p><em>At this time, the CSS Working Group does not envisage further work on this specification and does not plan to propose it as a W3C Recommendation.</em></p> </div> <div data-fill-with="at-risk"></div> <nav data-fill-with="table-of-contents" id="toc"> <h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2> <ol class="toc" role="directory"> <li><a href="#introduction"><span class="secno">1</span> <span class="content">Introduction</span></a> <li><a href="#conf"><span class="secno">2</span> <span class="content">Conformance</span></a> <li><a href="#selectors"><span class="secno">3</span> <span class="content">Selectors</span></a> <li><a href="#at-rules"><span class="secno">4</span> <span class="content">At-rules</span></a> <li><a href="#properties"><span class="secno">5</span> <span class="content">Properties</span></a> <li><a href="#syntax"><span class="secno">6</span> <span class="content">Syntax</span></a> <li><a href="#acknow"><span class="secno"></span> <span class="content">Acknowledgments</span></a> <li> <a href="#w3c-conformance"><span class="secno"></span> <span class="content"> Conformance</span></a> <ol class="toc"> <li><a href="#w3c-conventions"><span class="secno"></span> <span class="content"> Document conventions</span></a> <li><a href="#w3c-conformance-classes"><span class="secno"></span> <span class="content"> Conformance classes</span></a> <li> <a href="#w3c-partial"><span class="secno"></span> <span class="content"> Partial implementations</span></a> <ol class="toc"> <li><a href="#w3c-conform-future-proofing"><span class="secno"></span> <span class="content"> Implementations of Unstable and Proprietary Features</span></a> </ol> <li><a href="#w3c-testing"><span class="secno"></span> <span class="content"> Non-experimental implementations</span></a> </ol> <li> <a href="#references"><span class="secno"></span> <span class="content">References</span></a> <ol class="toc"> <li><a href="#normative"><span class="secno"></span> <span class="content">Normative References</span></a> <li><a href="#informative"><span class="secno"></span> <span class="content">Informative References</span></a> </ol> </ol> </nav> <main> <h2 class="heading settled" data-level="1" id="introduction"><span class="secno">1. </span><span class="content">Introduction</span><a class="self-link" href="#introduction"></a></h2> <p>This document specifies a profile of <abbr title="Cascading Style Sheets">CSS</abbr> that is in general based on <abbr title="Cascading Style Sheets">CSS</abbr> 2.1 <a data-link-type="biblio" href="#biblio-css21" title="Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification">[CSS21]</a>, but requires as well new features from <abbr title="Cascading Style Sheets">CSS</abbr> 3. In addition the document defines an <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> feature set, that is suggested to be implemented by more advanced user agents.</p> <h2 class="heading settled" data-level="2" id="conf"><span class="secno">2. </span><span class="content">Conformance</span><a class="self-link" href="#conf"></a></h2> <p> The key words of descriptive assertions and RFC 2119 terminology. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 <a data-link-type="biblio" href="#biblio-rfc2119" title="Key words for use in RFCs to Indicate Requirement Levels">[RFC2119]</a>. </p> <p> Since the goal of this specification is to define a baseline interoperability level, user agents <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> accept <abbr title="Cascading Style Sheets">CSS</abbr> documents conforming to <abbr title="Cascading Style Sheets">CSS</abbr> 2.1 or subsequent revisions of the <abbr title="Cascading Style Sheets">CSS</abbr> family of Recommendations. </p> <p> In order to conform to this specification, user agents, authoring tools, and content <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> conform to the <a href="http://www.w3.org/TR/CSS21/conform.html#conformance">Conformance</a> and <a href="http://www.w3.org/TR/CSS21/conform.html#errors">Error conditions</a> section of the <abbr title="Cascading Style Sheets">CSS</abbr> 2.1 specification <a data-link-type="biblio" href="#biblio-css21" title="Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification">[CSS21]</a>, with the following modifications. </p> <ol> <li> Only features marked as supported in this specification are <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>. Aside of the <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED </em> feature set, an additional <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> feature set is given, that may be implemented by more advanced user agents. This feature set is <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> by the <abbr title="Compound Document Formats">CDF</abbr> as in <a data-link-type="biblio" href="#biblio-wicdmobile10" title="WICD Mobile 1.0">[WICDMobile10]</a>. Support for a larger set of <abbr title="Cascading Style Sheets">CSS</abbr> 2.1 is <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>. <li> The requirement concerning which <a href="http://www.w3.org/TR/CSS21/media.html"><abbr title="Cascading Style Sheets">CSS</abbr> 2.1 media types</a> are supported is tightened so that both the <code>handheld</code> and <code>all</code> media types <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be accepted and processed. Other media types <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be accepted and processed as well. <li> The requirements that user agents <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> make it possible to select an alternate style sheet amongst those linked from the document, as well as provide for a way to turn off author style sheets, are relaxed to be <em class="rfc2119" title="Keyword in RFC 2119 context">RECOMMENDED</em> behavior, but not <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>. </ol> <h2 class="heading settled" data-level="3" id="selectors"><span class="secno">3. </span><span class="content">Selectors</span><a class="self-link" href="#selectors"></a></h2> <p> Selectors are defined in the <a href="http://www.w3.org/TR/CSS21/selector.html">Selectors</a> chapter of the <abbr title="Cascading Style Sheets">CSS</abbr> 2.1 specification <a data-link-type="biblio" href="#biblio-css21" title="Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification">[CSS21]</a>. The following table identifies which selector constructs <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be supported amongst those defined by <abbr title="Cascading Style Sheets">CSS</abbr> 2.1. </p> <table class="features" summary="Selectors of CSS mobile profile 2.0"> <tbody> <tr> <th>Selector type <th>Example <th>Meaning <th>Conformance <tr> <td><a href="http://www.w3.org/TR/CSS21/selector.html#universal-selector">Universal selector</a> <td><code>*</code> <td>Matches any element. <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td><a href="http://www.w3.org/TR/CSS21/selector.html#type-selectors">Type selectors</a> <td><code>E</code> <td>Matches any E element. <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td><a href="http://www.w3.org/TR/CSS21/selector.html#descendant-selectors">Descendant selectors</a> <td><code>E F</code> <td>Matches any F element that is a descendant of an E element. <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td><a href="http://www.w3.org/TR/CSS21/selector.html#child-selectors">Child selectors</a> <td><code>E > F</code> <td>Matches any F element that is a child of an element E. <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td><a href="http://www.w3.org/TR/CSS21/selector.html#link-pseudo-classes">The link pseudo-classes</a> <td><code>E:link</code> <td>Matches element E if E is the source anchor of a hyperlink, unvisited by a user. <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td><a href="http://www.w3.org/TR/CSS21/selector.html#link-pseudo-classes">The link pseudo-classes</a> <td><code>E:visited</code> <td>Matches element E if E is the source anchor of a hyperlink, visited by a user. <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td><a href="http://www.w3.org/TR/CSS21/selector.html#dynamic-pseudo-classes">The dynamic pseudo-classes</a> <td><code>E:active</code> <td>Matches element E if E is being activated by the user. <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td><a href="http://www.w3.org/TR/CSS21/selector.html#dynamic-pseudo-classes">The dynamic pseudo-classes</a> <td><code>E:focus</code> <td>Matches element E if E has the focus (accepts keyboard events or other forms of text input). <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td><a href="http://www.w3.org/TR/CSS21/selector.html#class-html">Class selectors</a> <td><code>.warning</code> <td> <em>Language specific</em>. (In (X)HTML, matches elements whose <code>class</code> attribute contains a token with the same name.) <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td><a href="http://www.w3.org/TR/CSS21/selector.html#id-selectors">ID selectors</a> <td><code>#myid</code> <td>Matches any element with an ID equal to "myid". <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td><a href="http://www.w3.org/TR/CSS21/selector.html#grouping">Grouping</a> <td><code>E1, E2, E3 { ... }</code> <td>Matches a group of elements, which share the same style declarations. <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> </table> <h2 class="heading settled" data-level="4" id="at-rules"><span class="secno">4. </span><span class="content">At-rules</span><a class="self-link" href="#at-rules"></a></h2> <p> At-rules are defined in the <a href="http://www.w3.org/TR/CSS21/syndata.html#at-rules">at-rules</a> section of the <abbr title="Cascading Style Sheets">CSS</abbr> 2.1 specification <a data-link-type="biblio" href="#biblio-css21" title="Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification">[CSS21]</a>. The following table identifies which at-rule constructs <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be supported amongst those defined by <abbr title="Cascading Style Sheets">CSS</abbr> by setting the at-rule as <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> in the table’s last column. Only at-rules that are part of the suggested feature set for advanced user agents are listed here as <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>. </p> <table class="features" summary="At-rules of CSS mobile profile 2.0"> <tbody> <tr> <th>Rule <th>Definition <th>Conformance <tr> <td><a href="http://www.w3.org/TR/CSS21/syndata.html#charset">@charset</a> <td>Defines character encoding for the style sheet. <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td><a href="http://www.w3.org/TR/CSS21/cascade.html#at-import">@import</a> <td>Imports an external style sheet. <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td><a href="http://www.w3.org/TR/CSS21/media.html#at-media-rule">@media</a> <td>Groups a set of style rules to apply only to one or more particular media. <br>Only the <code>handheld</code> and <code>all</code> media types <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be accepted and processed. Other media types <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be accepted and processed as well. <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr class="optional"> <td><a href="http://www.w3.org/TR/css3-namespace/#declaration">@namespace</a> <td>For declaring the default namespace and binding namespaces to namespace prefixes. <td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> </table> <h2 class="heading settled" data-level="5" id="properties"><span class="secno">5. </span><span class="content">Properties</span><a class="self-link" href="#properties"></a></h2> <p> Properties are defined in several chapters of the <abbr title="Cascading Style Sheets">CSS</abbr> 2.1 specification <a data-link-type="biblio" href="#biblio-css21" title="Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification">[CSS21]</a> and in case of marquee properties in the <abbr title="Cascading Style Sheets">CSS</abbr> Marquee Module <a data-link-type="biblio" href="#biblio-css3marquee" title="CSS Marquee Module Level 3">[CSS3MARQUEE]</a>. The following table identifies which properties <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be supported amongst those defined by <abbr title="Cascading Style Sheets">CSS</abbr> by setting the property as <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> in the table’s last column. Only properties that are part of the suggested feature set for advanced user agents are listed here as <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>. The property syntax is provided (expressed using the same <a href="http://www.w3.org/TR/CSS21/about.html#value-defs">value specifications</a> as <abbr title="Cascading Style Sheets">CSS</abbr> 2.1) when it is subsetted from the original. Limitations that apply to a property apply equally to its shorthand alternative. </p> <table class="features" summary="Properties of CSS mobile profile 2.0"> <tbody> <tr> <th>Property <th>Syntax (if different from <abbr title="Cascading Style Sheets">CSS</abbr>) <th>Conformance <tr> <td> <a href="http://www.w3.org/TR/CSS21/colors.html#propdef-background-color">background-color</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/colors.html#propdef-background-image">background-image</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/colors.html#propdef-background-repeat">background-repeat</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/colors.html#propdef-background-attachment">background-attachment</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/colors.html#propdef-background-position">background-position</a> <td><code>top | center | bottom | left | right | inherit</code> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/colors.html#propdef-background">background</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-top-width">border-top-width</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-right-width">border-right-width</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-bottom-width">border-bottom-width</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-left-width">border-left-width</a><br> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-width">border-width</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-top-color">border-top-color</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-right-color">border-right-color</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-bottom-color">border-bottom-color</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-left-color">border-left-color</a><br> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-color">border-color</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-top-style">border-top-style</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-right-style">border-right-style</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-bottom-style">border-bottom-style</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-left-style">border-left-style</a><br> <td><code>none | solid | dashed | dotted | inherit</code> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-style">border-style</a> <td><code>none | solid | dashed | dotted | inherit</code> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-top">border-top</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-right">border-right</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-bottom">border-bottom</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-left">border-left</a><br> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border">border</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr class="optional"> <td> <a href="http://www.w3.org/TR/CSS21/visuren.html#position-props">bottom</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/visuren.html#propdef-clear">clear</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/colors.html#propdef-color">color</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/visuren.html#propdef-display">display</a> <td><code>inline | block | list-item | none | inherit</code> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/visuren.html#propdef-float">float</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/fonts.html#propdef-font-family">font-family</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/fonts.html#propdef-font-style">font-style</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/fonts.html#propdef-font-variant">font-variant</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/fonts.html#propdef-font-weight">font-weight</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/fonts.html#propdef-font-size">font-size</a> <td><code><absolute-size> | <relative-size> | inherit</code> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/fonts.html#propdef-font">font</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/visudet.html#propdef-height">height</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr class="optional"> <td> <a href="http://www.w3.org/TR/CSS21/visuren.html#position-props">left</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/generate.html#propdef-list-style-type">list-style-type</a> <td> <code>disc | circle | square | decimal | lower-roman | upper-roman | lower-alpha | upper-alpha | none | inherit</code> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/generate.html#propdef-list-style-image">list-style-image</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/generate.html#propdef-list-style">list-style</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-margin-top">margin-top</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-margin-right">margin-right</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-margin-bottom">margin-bottom</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-margin-left">margin-left</a><br> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-margin">margin</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> marquee-direction <a data-link-type="biblio" href="#biblio-css3marquee" title="CSS Marquee Module Level 3">[CSS3MARQUEE]</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> marquee-loop <a data-link-type="biblio" href="#biblio-css3marquee" title="CSS Marquee Module Level 3">[CSS3MARQUEE]</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td>marquee-speed <a data-link-type="biblio" href="#biblio-css3marquee" title="CSS Marquee Module Level 3">[CSS3MARQUEE]</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td>marquee-style <a data-link-type="biblio" href="#biblio-css3marquee" title="CSS Marquee Module Level 3">[CSS3MARQUEE]</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/visudet.html#propdef-max-height">max-height</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/visudet.html#propdef-max-width">max-width</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/visudet.html#propdef-min-height">min-height</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/visudet.html#propdef-min-width">min-width</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr class="optional"> <td> <a href="http://www.w3.org/TR/CSS21/ui.html#propdef-outline-color">outline-color</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> <tr class="optional"> <td> <a href="http://www.w3.org/TR/CSS21/ui.html#propdef-outline-style">outline-style</a> <td><code>none | solid | dashed | dotted | inherit</code> <td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> <tr class="optional"> <td> <a href="http://www.w3.org/TR/CSS21/ui.html#propdef-outline-width">outline-width</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> <tr class="optional"> <td> <a href="http://www.w3.org/TR/CSS21/ui.html#dynamic-outlines">outline</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> <tr> <td> overflow <a data-link-type="biblio" href="#biblio-css21" title="Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification">[CSS21]</a> <td>auto <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> overflow-style <a data-link-type="biblio" href="#biblio-css3marquee" title="CSS Marquee Module Level 3">[CSS3MARQUEE]</a> <td>marquee <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-padding-top">padding-top</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-padding-right">padding-right</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-padding-bottom">padding-bottom</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-padding-left">padding-left</a><br> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-padding">padding</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr class="optional"> <td> <a href="http://www.w3.org/TR/CSS21/visuren.html#choose-position">position</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> <tr class="optional"> <td> <a href="http://www.w3.org/TR/CSS21/visuren.html#position-props">right</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/text.html#propdef-text-indent">text-indent</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/text.html#propdef-text-align">text-align</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/text.html#propdef-text-decoration">text-decoration</a> <td><code>none | blink |underline | inherit</code> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/text.html#propdef-text-transform">text-transform</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr class="optional"> <td> <a href="http://www.w3.org/TR/CSS21/visuren.html#position-props">top</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/visudet.html#propdef-vertical-align">vertical-align</a> <td><code>top | middle | bottom | baseline | inherit</code> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/visufx.html#propdef-visibility">visibility</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/text.html#propdef-white-space">white-space</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr> <td> <a href="http://www.w3.org/TR/CSS21/visudet.html#propdef-width">width</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> <tr class="optional"> <td> <a href="http://www.w3.org/TR/CSS21/visuren.html#z-index">z-index</a> <td> <td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> </table> <h3 class="no-num no-toc heading settled" id="informative-note"><span class="content">Informative Notes</span><a class="self-link" href="#informative-note"></a></h3> <ul> <li id="css-best-practise"><a class="self-link" href="#css-best-practise"></a> Content Providers will reach a larger and more satisfied audience by following Mobile Web Best Practices <a data-link-type="biblio" href="#biblio-mobile-bp" title="Mobile Web Best Practices 1.0">[MOBILE-BP]</a> and <abbr title="Cascading Style Sheets">CSS</abbr> Techniques for Web Content Accessibility Guidelines <a data-link-type="biblio" href="#biblio-wcag10-css-techs" title="CSS Techniques for Web Content Accessibility Guidelines 1.0">[WCAG10-CSS-TECHS]</a>. <li id="wcss-extensions"><a class="self-link" href="#wcss-extensions"></a> The <abbr title="Open Mobile Alliance">OMA</abbr> Wireless <abbr title="Cascading Style Sheets">CSS</abbr> 1.1 <a data-link-type="biblio" href="#biblio-wcss11" title="Wireless CSS Specification.">[WCSS11]</a> introduced three extensions <code>Marquee</code>, <code>Access Keys</code> and <code>Input</code>. Those extensions are deprecated in <abbr title="Open Mobile Alliance">OMA</abbr> Wireless <abbr title="Cascading Style Sheets">CSS</abbr> 1.2 <a data-link-type="biblio" href="#biblio-wcss12" title="Wireless CSS Specification Version 1.2.">[WCSS12]</a>. The <code>Marquee</code> functionality has been redefined by the marquee properties of the <abbr title="Cascading Style Sheets">CSS</abbr> 3 box model <a data-link-type="biblio" href="#biblio-css3marquee" title="CSS Marquee Module Level 3">[CSS3MARQUEE]</a> </ul> <h2 class="heading settled" data-level="6" id="syntax"><span class="secno">6. </span><span class="content">Syntax</span><a class="self-link" href="#syntax"></a></h2> <p> A user agent <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> support all value types defined in the <a href="http://www.w3.org/TR/CSS21/syndata.html#values">Values</a> section of the <abbr title="Cascading Style Sheets">CSS</abbr> 2.1 specification <a data-link-type="biblio" href="#biblio-css21" title="Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification">[CSS21]</a>, with the following exceptions: </p> <ol> <li>Support for <a href="http://www.w3.org/TR/CSS21/syndata.html#counter">counter values</a> is <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> <li> Support for <a href="http://www.w3.org/TR/CSS21/ui.html#system-colors">CSS2 System Colors</a> and <a href="http://www.w3.org/TR/CSS21/ui.html#system-fonts">User preferences for fonts</a> is <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>. </ol> <h2 class="no-num heading settled" id="acknow"><span class="content">Acknowledgments</span><a class="self-link" href="#acknow"></a></h2> <p> The editors wish to thank the authors of the previous version of this document, Ted Wugofski (Openwave), Doug Dominiak (Openwave, formerly Motorola), Peter Stark (Ericsson), and Tapas Roy (Openwave), as well as the authors of the <abbr title="Open Mobile Alliance">OMA</abbr> Wireless <abbr title="Cascading Style Sheets">CSS</abbr> specifications and the <abbr title="Cascading Style Sheets">CSS</abbr> 2.1 specification. Furthermore, the editors want to thank the <abbr title="Compound Document Formats">CDF</abbr> <abbr title="Working Group">WG</abbr> for their participation on this specification. </p> </main> <h2 class="no-ref no-num heading settled" id="w3c-conformance"><span class="content"> Conformance</span><a class="self-link" href="#w3c-conformance"></a></h2> <h3 class="no-ref heading settled" id="w3c-conventions"><span class="content"> Document conventions</span><a class="self-link" href="#w3c-conventions"></a></h3> <p>Conformance requirements are expressed with a combination of descriptive assertions and RFC 2119 terminology. The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this document are to be interpreted as described in RFC 2119. However, for readability, these words do not appear in all uppercase letters in this specification. </p> <p>All of the text of this specification is normative except sections explicitly marked as non-normative, examples, and notes. <a data-link-type="biblio" href="#biblio-rfc2119" title="Key words for use in RFCs to Indicate Requirement Levels">[RFC2119]</a></p> <p>Examples in this specification are introduced with the words “for example” or are set apart from the normative text with <code>class="example"</code>, like this: </p> <div class="example" id="w3c-example"> <a class="self-link" href="#w3c-example"></a> <p>This is an example of an informative example.</p> </div> <p>Informative notes begin with the word “Note” and are set apart from the normative text with <code>class="note"</code>, like this: </p> <p class="note" role="note">Note, this is an informative note.</p> <p>Advisements are normative sections styled to evoke special attention and are set apart from other normative text with <code><strong class="advisement"></code>, like this: <strong class="advisement"> UAs MUST provide an accessible alternative. </strong></p> <details class="wpt-tests-block" dir="ltr" lang="en" open> <summary>Tests</summary> <p>Tests relating to the content of this specification may be documented in “Tests” blocks like this one. Any such block is non-normative.</p> <ul class="wpt-tests-list"></ul> <hr> </details> <h3 class="no-ref heading settled" id="w3c-conformance-classes"><span class="content"> Conformance classes</span><a class="self-link" href="#w3c-conformance-classes"></a></h3> <p>Conformance to this specification is defined for three conformance classes: </p> <dl> <dt>style sheet <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS style sheet</a>. <dt>renderer <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a> that interprets the semantics of a style sheet and renders documents that use them. <dt>authoring tool <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a> that writes a style sheet. </dl> <p>A style sheet is conformant to this specification if all of its statements that use syntax defined in this module are valid according to the generic CSS grammar and the individual grammars of each feature defined in this module. </p> <p>A renderer is conformant to this specification if, in addition to interpreting the style sheet as defined by the appropriate specifications, it supports all the features defined by this specification by parsing them correctly and rendering the document accordingly. However, the inability of a UA to correctly render a document due to limitations of the device does not make the UA non-conformant. (For example, a UA is not required to render color on a monochrome monitor.) </p> <p>An authoring tool is conformant to this specification if it writes style sheets that are syntactically correct according to the generic CSS grammar and the individual grammars of each feature in this module, and meet all other conformance requirements of style sheets as described in this module. </p> <h3 class="no-ref heading settled" id="w3c-partial"><span class="content"> Partial implementations</span><a class="self-link" href="#w3c-partial"></a></h3> <p>So that authors can exploit the forward-compatible parsing rules to assign fallback values, CSS renderers <strong>must</strong> treat as invalid (and <a href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignore as appropriate</a>) any at-rules, properties, property values, keywords, and other syntactic constructs for which they have no usable level of support. In particular, user agents <strong>must not</strong> selectively ignore unsupported component values and honor supported values in a single multi-value property declaration: if any value is considered invalid (as unsupported values must be), CSS requires that the entire declaration be ignored.</p> <h4 class="heading settled" id="w3c-conform-future-proofing"><span class="content"> Implementations of Unstable and Proprietary Features</span><a class="self-link" href="#w3c-conform-future-proofing"></a></h4> <p>To avoid clashes with future stable CSS features, the CSSWG recommends <a href="http://www.w3.org/TR/CSS/#future-proofing">following best practices</a> for the implementation of <a href="http://www.w3.org/TR/CSS/#unstable">unstable</a> features and <a href="http://www.w3.org/TR/CSS/#proprietary-extension">proprietary extensions</a> to CSS. </p> <h3 class="no-ref heading settled" id="w3c-testing"><span class="content"> Non-experimental implementations</span><a class="self-link" href="#w3c-testing"></a></h3> <p>Once a specification reaches the Candidate Recommendation stage, non-experimental implementations are possible, and implementors should release an unprefixed implementation of any CR-level feature they can demonstrate to be correctly implemented according to spec. </p> <p>To establish and maintain the interoperability of CSS across implementations, the CSS Working Group requests that non-experimental CSS renderers submit an implementation report (and, if necessary, the testcases used for that implementation report) to the W3C before releasing an unprefixed implementation of any CSS features. Testcases submitted to W3C are subject to review and correction by the CSS Working Group. </p> <p>Further information on submitting testcases and implementation reports can be found from on the CSS Working Group’s website at <a href="http://www.w3.org/Style/CSS/Test/">http://www.w3.org/Style/CSS/Test/</a>. Questions should be directed to the <a href="http://lists.w3.org/Archives/Public/public-css-testsuite">public-css-testsuite@w3.org</a> mailing list.</p> <script src="https://www.w3.org/scripts/TR/2021/fixup.js"></script> <h2 class="no-num no-ref heading settled" id="references"><span class="content">References</span><a class="self-link" href="#references"></a></h2> <h3 class="no-num no-ref heading settled" id="normative"><span class="content">Normative References</span><a class="self-link" href="#normative"></a></h3> <dl> <dt id="biblio-css21">[CSS21] <dd>Bert Bos; et al. <a href="https://www.w3.org/TR/CSS21/"><cite>Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification</cite></a>. 7 June 2011. REC. URL: <a href="https://www.w3.org/TR/CSS21/">https://www.w3.org/TR/CSS21/</a> <dt id="biblio-css3marquee">[CSS3MARQUEE] <dd>Bert Bos. <a href="https://www.w3.org/TR/css3-marquee/"><cite>CSS Marquee Module Level 3</cite></a>. 14 October 2014. NOTE. URL: <a href="https://www.w3.org/TR/css3-marquee/">https://www.w3.org/TR/css3-marquee/</a> <dt id="biblio-rfc2119">[RFC2119] <dd>S. Bradner. <a href="https://datatracker.ietf.org/doc/html/rfc2119"><cite>Key words for use in RFCs to Indicate Requirement Levels</cite></a>. March 1997. Best Current Practice. URL: <a href="https://datatracker.ietf.org/doc/html/rfc2119">https://datatracker.ietf.org/doc/html/rfc2119</a> <dt id="biblio-wicdmobile10">[WICDMobile10] <dd>Timur Mehrvarz; et al. <a href="https://www.w3.org/TR/WICDMobile/"><cite>WICD Mobile 1.0</cite></a>. 19 August 2010. NOTE. URL: <a href="https://www.w3.org/TR/WICDMobile/">https://www.w3.org/TR/WICDMobile/</a> </dl> <h3 class="no-num no-ref heading settled" id="informative"><span class="content">Informative References</span><a class="self-link" href="#informative"></a></h3> <dl> <dt id="biblio-mobile-bp">[MOBILE-BP] <dd>Jo Rabin; Charles McCathieNevile. <a href="https://www.w3.org/TR/mobile-bp/"><cite>Mobile Web Best Practices 1.0</cite></a>. 29 July 2008. REC. URL: <a href="https://www.w3.org/TR/mobile-bp/">https://www.w3.org/TR/mobile-bp/</a> <dt id="biblio-wcag10-css-techs">[WCAG10-CSS-TECHS] <dd>Wendy Chisholm; Gregg Vanderheiden; Ian Jacobs. <a href="https://www.w3.org/TR/WCAG10-CSS-TECHS/"><cite>CSS Techniques for Web Content Accessibility Guidelines 1.0</cite></a>. 6 November 2000. NOTE. URL: <a href="https://www.w3.org/TR/WCAG10-CSS-TECHS/">https://www.w3.org/TR/WCAG10-CSS-TECHS/</a> <dt id="biblio-wcss11">[WCSS11] <dd>Open Mobile Alliance. <a href="http://www.openmobilealliance.org/technical/release_program/docs/Browsing/V2_3-20080331-A/OMA-WAP-WCSS-V1_1-20061020-A.pdf"><cite>Wireless CSS Specification.</cite></a> October 2006. Approved Version 1.1. URL: <a href="http://www.openmobilealliance.org/technical/release_program/docs/Browsing/V2_3-20080331-A/OMA-WAP-WCSS-V1_1-20061020-A.pdf">http://www.openmobilealliance.org/technical/release_program/docs/Browsing/V2_3-20080331-A/OMA-WAP-WCSS-V1_1-20061020-A.pdf</a> <dt id="biblio-wcss12">[WCSS12] <dd>Open Mobile Alliance. <a href="http://www.openmobilealliance.org/ftp/Public_documents/MCE/MAE/Permanent_documents/OMA-TS-WCSS-V1_2-20070921-D.zip"><cite>Wireless CSS Specification Version 1.2.</cite></a> 21 September 2007. (Work in progress.) URL: <a href="http://www.openmobilealliance.org/ftp/Public_documents/MCE/MAE/Permanent_documents/OMA-TS-WCSS-V1_2-20070921-D.zip">http://www.openmobilealliance.org/ftp/Public_documents/MCE/MAE/Permanent_documents/OMA-TS-WCSS-V1_2-20070921-D.zip</a> </dl>