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66 <body>
68 <p><a href="http://www.w3.org/"><img height=48 alt=W3C src="http://www.w3.org/Icons/w3c_home" width=72></a>
74 <dl>
76 <dt>This version:
81 <dt>Latest version:
84 http://www.w3.org/TR/css3-selectors</a>
86 <dt>Previous version:
95 <dd class="vcard"><a lang="tr" class="url fn" href="http://www.tantek.com/">Tantek Çelik</a> (Invited Expert)
103 <dd class="vcard"><span class="fn">John Williams</span> (former editor, <span class="company"><a
106 </dl>
117 <a
119 <a
121 <a
123 use</a> rules apply.
127 </div>
132 tree. Selectors have been optimized for use with HTML and XML, and
133 are designed to be usable in performance-critical code.</p>
136 Style Sheets) is a language for describing the rendering of <acronym
139 screen, on paper, in speech, etc. CSS uses Selectors for binding
140 style properties to elements in the document. This document
141 describes extensions to the selectors defined in CSS level 2. These
142 extended selectors will be used by CSS level 3.
148 <p>That is, given an element and a selector, this specification
149 defines whether that element matches the selector.</p>
151 <p>These expressions can also be used, for instance, to select a set
152 of elements, or a single element from a set of elements, by
153 evaluating the expression across all the elements in a
160 <p><em>This section describes the status of this document at the
161 time of its publication. Other documents may supersede this
162 document. A list of current W3C publications and the latest revision
163 of this technical report can be found in the <a
165 http://www.w3.org/TR/.</a></em></p>
173 <p>The CSS Working Group doesn't expect that all implementations of
174 CSS3 will have to implement all selectors. Instead, there will
175 probably be a small number of variants of CSS3, called profiles. For
176 example, it may be that only a profile for interactive user agents
177 will include all of the selectors.</p>
182 document is a revision of the <a
185 implementation feedback received in the past few years. It is
186 expected that this last call will proceed straight to Proposed
187 Recommendation stage since it is believed that interoperability will
188 be demonstrable.</p>
190 <p>All persons are encouraged to review and implement this
191 specification and return comments to the (<a
193 public mailing list <a
196 Members can also send comments directly to the CSS Working
197 Group.
200 <p>This is still a draft document and may be updated, replaced, or
201 obsoleted by other documents at any time. It is inappropriate to
206 The English version of this specification is the only normative
207 version.
215 <ul>
219 </ul>
229 </ul>
231 <ul>
233 </ul>
236 <li class="tocline4"><a href="#attribute-representation">6.3.1. Representation of attributes and attributes values</a>
240 </ul>
250 <ul>
263 </ul>
265 </ul>
266 </li>
267 </ul>
269 <ul>
274 </ul>
281 <li class="tocline4"><a href="#adjacent-sibling-combinators">8.3.1. Adjacent sibling combinator</a>
282 <li class="tocline4"><a href="#general-sibling-combinators">8.3.2. General sibling combinator</a></li>
283 </ul>
284 </li>
285 </ul>
291 </ul>
298 </ul>
300 </div>
306 <p>Some features of this specification are specific to CSS, or have
307 particular limitations or rules specific to CSS. In this
308 specification, these have been described in terms of CSS2.1. <a
313 <p>All of the text of this specification is normative except
314 examples, notes, and sections explicitly marked as
315 non-normative.</p>
321 <p>The main differences between the selectors in CSS2 and those in
322 Selectors are:
324 <ul>
326 <li>the list of basic definitions (selector, group of selectors,
327 simple selector, etc.) has been changed; in particular, what was
328 referred to in CSS2 as a simple selector is now called a sequence
329 of simple selectors, and the term "simple selector" is now used for
330 the components of this sequence</li>
332 <li>an optional namespace component is now allowed in type element
333 selectors, the universal selector and attribute selectors</li>
337 <li>new simple selectors including substring matching attribute
338 selectors, and new pseudo-classes</li>
341 for pseudo-elements</li>
345 <li>profiles to be added to specifications integrating Selectors
346 and defining the set of selectors which is actually supported by
347 each specification</li>
349 <li>Selectors are now a CSS3 Module and an independent
350 specification; other specifications can now refer to this document
351 independently of CSS</li>
355 </ul>
359 <p><em>This section is non-normative, as it merely summarizes the
360 following sections.</em></p>
362 <p>A Selector represents a structure. This structure can be used as a
363 condition (e.g. in a CSS rule) that determines which elements a
364 selector matches in the document tree, or as a flat description of the
365 HTML or XML fragment corresponding to that structure.</p>
367 <p>Selectors may range from simple element names to rich contextual
368 representations.</p>
373 <thead>
374 <tr>
379 <tbody>
380 <tr>
385 selector</a></td>
387 <tr>
393 <tr>
398 selectors</a></td>
400 <tr>
406 selectors</a></td>
408 <tr>
414 selectors</a></td>
416 <tr>
422 selectors</a></td>
424 <tr>
430 selectors</a></td>
432 <tr>
438 selectors</a></td>
440 <tr>
446 selectors</a></td>
448 <tr>
453 pseudo-classes</a></td>
455 <tr>
460 pseudo-classes</a></td>
462 <tr>
465 from the last one</td>
468 pseudo-classes</a></td>
470 <tr>
475 pseudo-classes</a></td>
477 <tr>
480 from the last one</td>
483 pseudo-classes</a></td>
485 <tr>
490 pseudo-classes</a></td>
492 <tr>
497 pseudo-classes</a></td>
499 <tr>
504 pseudo-classes</a></td>
506 <tr>
511 pseudo-classes</a></td>
513 <tr>
518 pseudo-classes</a></td>
520 <tr>
525 pseudo-classes</a></td>
527 <tr>
530 nodes)</td>
533 pseudo-classes</a></td>
535 <tr>
538 which the target is not yet visited (:link) or already visited
539 (:visited)</td>
542 pseudo-classes</a></td>
544 <tr>
549 action pseudo-classes</a></td>
551 <tr>
556 pseudo-class</a></td>
558 <tr>
561 language specifies how language is determined)</td>
564 pseudo-class</a></td>
566 <tr>
569 disabled</td>
572 pseudo-classes</a></td>
574 <tr>
580 pseudo-classes</a></td>
582 <tr>
587 pseudo-element</a></td>
589 <tr>
594 pseudo-element</a></td>
596 <tr>
599 selected/highlighted by the user</td>
602 fragments pseudo-elements</a></td>
604 <tr>
609 pseudo-element</a></td>
611 <tr>
616 pseudo-element</a></td>
618 <tr>
624 selectors</a></td>
626 <tr>
631 selectors</a></td>
633 <tr>
638 pseudo-class</a></td>
640 <tr>
645 combinator</a></td>
647 <tr>
652 combinator</a></td>
654 <tr>
660 <tr>
667 <p>The meaning of each selector is derived from the table above by
669 column.</p>
673 <p>The case sensitivity of document language element names, attribute
674 names, and attribute values in selectors depends on the document
675 language. For example, in HTML, element names are case-insensitive,
676 but in XML, they are case-sensitive.</p>
689 selector or universal selector is allowed in the sequence.</p>
701 sequence of simple selectors.</p>
706 space may appear between a combinator and the simple selectors around
711 never part of white space.</p>
713 <p>The elements of a document tree that are represented by a selector
715 selector consisting of a single sequence of simple selectors
716 represents any element satisfying its requirements. Prepending another
717 sequence of simple selectors and a combinator to a sequence imposes
718 additional matching constraints, so the subjects of a selector are
719 always a subset of the elements represented by the last sequence of
720 simple selectors.</p>
722 <p>An empty selector, containing no sequence of simple selectors and
728 <p>When several selectors share the same declarations, they may be
733 <p>In this example, we condense three rules with identical
734 declarations into one. Thus,</p>
735 <pre>h1 { font-family: sans-serif }
736 h2 { font-family: sans-serif }
737 h3 { font-family: sans-serif }</pre>
740 </div>
743 because all the selectors are valid selectors. If just one of these
744 selectors were invalid, the entire group of selectors would be
745 invalid. This would invalidate the rule for all three heading
746 elements, whereas in the former case only one of the three individual
747 heading rules would be invalidated.</p>
755 element type. A type selector represents an instance of the element
756 type in the document tree.</p>
762 </div>
769 that has been previously declared may be prepended to the element name
773 <p>The namespace component may be left empty to indicate that the
774 selector is only to represent elements with no declared namespace.</p>
776 <p>An asterisk may be used for the namespace prefix, indicating that
777 the selector represents elements in any namespace (including elements
778 with no namespace).</p>
780 <p>Element type selectors that have no namespace component (no
781 namespace separator), represent elements without regard to the
782 element's namespace (equivalent to "<code>*|</code>") unless a default
783 namespace has been declared. If a default namespace has been declared,
784 the selector will represent only elements in the default
785 namespace.</p>
787 <p>A type selector containing a namespace prefix that has not been
789 The mechanism for declaring a namespace prefix is left up to the
790 language implementing Selectors. In CSS, such a mechanism is defined
791 in the General Syntax module.</p>
793 <p>In a namespace-aware client, element type selectors will only match
794 against the <a
796 of the element's <a
799 behaviors in down-level clients.</p>
803 <dl>
807 <dd>elements with name E in any namespace, including those without any
808 declared namespace</dd>
812 <dd>if no default namespace has been specified, this is equivalent to *|E.
813 Otherwise it is equivalent to ns|E where ns is the default namespace.</dd>
814 </dl>
819 <pre>@namespace foo url(http://www.example.com);
820 foo|h1 { color: blue }
821 foo|* { color: yellow }
822 |h1 { color: red }
823 *|h1 { color: green }
824 h1 { color: green }</pre>
829 <p>The second rule will match all elements in the
833 any declared namespace.</p>
836 namespace (including those without any declared namespace).</p>
838 <p>The last rule is equivalent to the fourth rule because no default
839 namespace has been defined.</p>
841 </div>
847 type. It represents any single element in the document tree in any
848 namespace (including those without any declared namespace) if no
849 default namespace has been specified. If a default namespace has been
853 <p>If the universal selector is not the only component of a sequence
858 <ul>
862 </ul>
863 </div>
867 omitted.</p>
871 <p>The universal selector allows an optional namespace component. It
872 is used as follows:</p>
874 <dl>
882 <dd>if no default namespace has been specified, this is equivalent to *|*.
883 Otherwise it is equivalent to ns|* where ns is the default namespace.</dd>
884 </dl>
886 <p>A universal selector containing a namespace prefix that has not
888 selector. The mechanism for declaring a namespace prefix is left up
889 to the language implementing Selectors. In CSS, such a mechanism is
890 defined in the General Syntax module.</p>
895 <p>Selectors allow the representation of an element's attributes. When
896 a selector is used as an expression to match against an element,
897 attribute selectors must be considered to match an element if that
898 element has an attribute that matches the attribute represented by the
899 attribute selector.</p>
902 selectors</a></h4>
906 <dl>
909 the attribute.</dd>
918 spaces).</dd>
928 </dl>
930 <p>Attribute values must be identifiers or strings. The
931 case-sensitivity of attribute names and values in selectors depends on
932 the document language.</p>
940 value:</p>
944 <p>In the following example, the selector represents a
950 <p>Multiple attribute selectors can be used to represent several
951 attributes of an element, or several conditions on the same
960 and "~=". The first selector will represent, for example, the value
980 <p>Similarly, the following selectors represents a
984 <pre>DIALOGUE[character=romeo]
985 DIALOGUE[character=juliet]</pre>
987 </div>
990 selectors</h4>
992 <p>Three additional attribute selectors are provided for matching
993 substrings in the value of an attribute:</p>
995 <dl>
1005 </dl>
1007 <p>Attribute values must be identifiers or strings. The
1008 case-sensitivity of attribute names in selectors depends on the
1009 document language.</p>
1014 image:</p>
1022 </div>
1026 <p>Attribute selectors allow an optional namespace component to the
1027 attribute name. A namespace prefix that has been previously declared
1028 may be prepended to the attribute name separated by the namespace
1030 the Namespaces in the XML recommendation, default namespaces do not
1031 apply to attributes, therefore attribute selectors without a namespace
1032 component apply only to attributes that have no declared namespace
1033 (equivalent to "<code>|attr</code>"). An asterisk may be used for the
1034 namespace prefix indicating that the selector is to match all
1035 attribute names without regard to the attribute's namespace.
1037 <p>An attribute selector with an attribute name containing a namespace
1038 prefix that has not been previously declared is an <a
1040 a namespace prefix is left up to the language implementing Selectors.
1041 In CSS, such a mechanism is defined in the General Syntax module.
1046 [foo|att=val] { color: blue }
1047 [*|att] { color: yellow }
1048 [|att] { color: green }
1049 [att] { color: green }</pre>
1051 <p>The first rule will match only elements with the attribute
1055 <p>The second rule will match only elements with the attribute
1057 (including no declared namespace).</p>
1059 <p>The last two rules are equivalent and will match only elements
1061 declared to be in a namespace.</p>
1063 </div>
1067 <p>Attribute selectors represent explicitly set attribute values in
1068 the document tree. Default attribute values may be defined in a DTD or
1069 elsewhere, but cannot always be selected by attribute
1070 selectors. Selectors should be designed so that they work even if the
1071 default values are not included in the document tree.</p>
1080 knowledge of that namespace to treat default attribute values as if
1081 they were present in the document. (For example, an XHTML UA is not
1082 required to use its built-in knowledge of the XHTML DTD.)</p>
1085 choose to ignore external subsets.</p>
1097 <pre>EXAMPLE[notation=decimal] { /*... default property settings ...*/ }
1098 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1101 is set by default, i.e. not set explicitly. To catch all cases, the
1102 attribute selector for the default value must be dropped:</p>
1104 <pre>EXAMPLE { /*... default property settings ...*/ }
1105 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1108 more specific than the tag
1109 selector alone, the style declarations in the second rule will override
1110 those in the first for elements that have a "notation" attribute value
1111 of "octal". Care has to be taken that all property declarations that
1112 are to apply only to the default case are overridden in the non-default
1113 cases' style rules.</p>
1115 </div>
1123 the same meaning. The attribute value must immediately follow the
1126 <p>UAs may apply selectors using the period (.) notation in XML
1127 documents if the UA has namespace-specific knowledge that allows it to
1129 respective namespace. One such example of namespace-specific knowledge
1130 is the prose in the specification for a particular namespace (e.g. SVG
1141 <p>We can assign style information to all elements with
1150 <p>The following assigns style only to H1 elements with
1155 <p>Given these rules, the first H1 instance below would not have
1156 green text, while the second would:</p>
1161 </div>
1171 has been assigned a list of <a
1181 </div>
1184 power to the "class" attribute, authors could conceivably design their
1185 own "document language" based on elements with almost no associated
1186 presentation (such as DIV and SPAN in HTML) and assigning style
1187 information through the "class" attribute. Authors should avoid this
1188 practice since the structural elements of a document language often
1189 have recognized and accepted meanings and author-defined classes may
1190 not.</p>
1193 class attributes, their values must be concatenated with spaces
1194 between the values before searching for the class. As of this time the
1195 working group is not aware of any manner in which this situation can
1196 be reached, however, so this behavior is explicitly non-normative in
1197 this specification.</p>
1201 <p>Document languages may contain attributes that are declared to be
1202 of type ID. What makes attributes of type ID special is that no two
1203 such attributes can have the same value in a document, regardless of
1204 the type of the elements that carry them; whatever the document
1205 language, an ID typed attribute can be used to uniquely identify its
1206 element. In HTML all ID attributes are named "id"; XML applications
1207 may name ID attributes differently, but the same restriction
1208 applies.</p>
1210 <p>An ID-typed attribute of a document language allows authors to
1211 assign an identifier to one element instance in the document tree. W3C
1212 ID selectors represent an element instance based on its identifier. An
1215 identifier.</p>
1217 <p>Selectors does not specify how a UA knows the ID-typed attribute of
1218 an element. The UA may, e.g., read a document's DTD, have the
1219 information hard-coded or ask the user.
1226 <p>The following ID selector represents any element whose ID-typed
1229 <p>The following selector represents any element whose ID-typed
1232 </div>
1236 contains an element's IDs is contained in a DTD or a schema. When
1237 parsing XML, UAs do not always read the DTD, and thus may not know
1238 what the ID of an element is (though a UA may have namespace-specific
1239 knowledge that allows it to determine which attribute is the ID
1240 attribute for that namespace). If a style sheet designer knows or
1241 suspects that a UA may not know what the ID of an element is, he
1242 should use normal attribute selectors instead:
1246 <p>If an element has multiple ID attributes, all of them must be
1247 treated as IDs for that element for the purposes of the ID
1248 selector. Such a situation could be reached using mixtures of xml:id,
1249 DOM3 Core, XML DTDs, and namespace-specific knowledge.</p>
1253 <p>The pseudo-class concept is introduced to permit selection based on
1254 information that lies outside of the document tree or that cannot be
1255 expressed using the other simple selectors.</p>
1259 optionally by a value between parentheses.</p>
1261 <p>Pseudo-classes are allowed in all sequences of simple selectors
1262 contained in a selector. Pseudo-classes are allowed anywhere in
1263 sequences of simple selectors, after the leading type selector or
1264 universal selector (possibly omitted). Pseudo-class names are
1265 case-insensitive. Some pseudo-classes are mutually exclusive, while
1266 others can be applied simultaneously to the same
1267 element. Pseudo-classes may be dynamic, in the sense that an element
1268 may acquire or lose a pseudo-class while a user interacts with the
1269 document.</p>
1274 <p>Dynamic pseudo-classes classify elements on characteristics other
1275 than their name, attributes, or content, in principle characteristics
1276 that cannot be deduced from the document tree.</p>
1278 <p>Dynamic pseudo-classes do not appear in the document source or
1279 document tree.</p>
1284 <p>User agents commonly display unvisited links differently from
1285 previously visited ones. Selectors
1289 <ul>
1291 not yet been visited.</li>
1293 been visited by the user. </li>
1294 </ul>
1296 <p>After some amount of time, user agents may choose to return a
1297 visited link to the (unvisited) ':link' state.</p>
1305 <p>The following selector represents links carrying class
1310 </div>
1313 authors to abuse the :link and :visited pseudo-classes to determine
1314 which sites a user has visited without the user's consent.
1316 <p>UAs may therefore treat all links as unvisited links, or implement
1317 other measures to preserve the user's privacy while rendering visited
1318 and unvisited links differently.</p>
1321 :hover, :active, and :focus</a></h5>
1323 <p>Interactive user agents sometimes change the rendering in response
1324 to user actions. Selectors provides
1325 three pseudo-classes for the selection of an element the user is
1326 acting on.</p>
1328 <ul>
1331 designates an element with a pointing device, but does not activate
1332 it. For example, a visual user agent could apply this pseudo-class
1333 when the cursor (mouse pointer) hovers over a box generated by the
1334 element. User agents not that do not support <a
1336 media</a> do not have to support this pseudo-class. Some conforming
1337 user agents that support <a
1339 media</a> may not be able to support this pseudo-class (e.g., a pen
1340 device that does not detect hovering).</li>
1343 is being activated by the user. For example, between the times the
1344 user presses the mouse button and releases it.</li>
1347 has the focus (accepts keyboard or mouse events, or other forms of
1348 input). </li>
1350 </ul>
1352 <p>There may be document language or implementation specific limits on
1356 <p>These pseudo-classes are not mutually exclusive. An element may
1357 match several pseudo-classes at the same time.</p>
1359 <p>Selectors doesn't define if the parent of an element that is
1360 ':active' or ':hover' is also in that state.</p>
1364 <pre>a:link /* unvisited links */
1365 a:visited /* visited links */
1366 a:hover /* user hovers */
1367 a:active /* active links */</pre>
1369 <pre>a:focus
1370 a:focus:hover</pre>
1372 the pseudo-class :focus and in the pseudo-class :hover.</p>
1373 </div>
1376 and ':active' (or ':link' and ':active').</p>
1380 <p>Some URIs refer to a location within a resource. This kind of URI
1382 identifier (called the fragment identifier).</p>
1384 <p>URIs with fragment identifiers link to a certain element within the
1385 document, known as the target element. For instance, here is a URI
1387 document:</p>
1392 pseudo-class. If the document's URI has no fragment identifier, then
1393 the document has no target element.</p>
1400 URI.</p>
1401 </div>
1406 target element red and place an image before it, if there is one:</p>
1407 <pre>*:target { color : red }
1408 *:target::before { content : url(target.png) }</pre>
1409 </div>
1413 <p>If the document language specifies how the human language of an
1414 element is determined, it is possible to write selectors that
1415 represent an element based on its language. For example, in HTML <a
1418 element, and possibly by information from the protocol (such as HTTP
1420 there may be other document language-specific methods for determining
1421 the language.</p>
1424 is in language C. Whether an element is represented by a
1426 being either equal to, or a hyphen-separated substring of, the
1427 element's language value, in the same way as if performed by the <a
1429 selectors. The identifier C does not have to be a valid language
1430 name.</p>
1444 <p>The two following selectors represent an HTML document that is in
1445 Belgian, French, or German. The two next selectors represent
1447 or German.</p>
1448 <pre>html:lang(fr-be)
1449 html:lang(de)
1450 :lang(fr-be) > q
1452 </div>
1459 the look of user interface elements that are enabled — which the
1460 user can select or activate in some fashion (e.g. clicking on a button
1461 with a mouse). There is a need for such a pseudo-class because there
1462 is no way to programmatically specify the default appearance of say,
1464 would look like when it was disabled.</p>
1467 author to specify precisely how a disabled or inactive user interface
1468 element should look.</p>
1470 <p>Most elements will be neither enabled nor disabled. An element is
1471 enabled if the user can either activate it or transfer the focus to
1472 it. An element is disabled if it could be enabled, but the user cannot
1473 presently activate it or transfer focus to it.</p>
1478 <p>Radio and checkbox elements can be toggled by the user. Some menu
1479 items are "checked" when the user selects them. When such elements are
1483 attributes as described in <a
1488 in nature, and is altered by user action, since it can also be based
1497 <p>Radio and checkbox elements can be toggled by the user, but are
1498 sometimes in an indeterminate state, neither checked nor unchecked.
1499 This can be due to an element attribute, or DOM manipulation.</p>
1501 <p>A future version of this specification may introduce an
1503 <!--While the <code>:indeterminate</code> pseudo-class is dynamic in
1504 nature, and is altered by user action, since it can also be based on
1505 the presence of an element attribute, it applies to all media.</p>
1507 <p>Components of a radio-group initialized with no pre-selected choice
1510 </div>
1516 pseudo-classes</dfn> to permit selection based on extra information that lies in
1517 the document tree but cannot be represented by other simple selectors or
1518 combinators.
1520 <p>Note that standalone pieces of PCDATA (text nodes in the DOM) are
1521 not counted when calculating the position of an element in the list of
1522 children of its parent. When calculating the position of an element in
1523 the list of children of its parent, the index numbering starts at 1.
1529 the root of the document. In HTML 4, this is always the
1535 <p>The
1537 pseudo-class notation represents an element that has
1543 each. For example, this allows the selectors to address every other
1544 row in a table, and could be used to alternate the color
1547 integers. The index of the first child of an element is 1.
1558 tr:nth-child(odd) /* same */
1559 tr:nth-child(2n) /* represents every even row of an HTML table */
1560 tr:nth-child(even) /* same */
1562 /* Alternate paragraph colours in CSS */
1567 </div>
1572 included, so the syntax simplifies to
1580 </div>
1588 bar:nth-child(n+0) /* same */
1589 bar:nth-child(n) /* same */
1591 </div>
1600 </div>
1603 pseudo-class represents no element in the document tree.</p>
1608 tree.</p>
1613 </div>
1616 expression must be removed (it is effectively replaced by the "-"
1624 </div>
1630 pseudo-class notation represents an element that has
1636 as arguments.
1643 foo:nth-last-child(odd) /* represents all odd foo elements in their parent element,
1644 counting from the last one */</pre>
1645 </div>
1651 pseudo-class notation represents an element that has
1656 of that type after all the children of that type have been split into
1658 for the syntax of its argument. It also accepts the
1667 </div>
1673 pseudo-class notation represents an element that has
1685 following selector:</p>
1688 selector ends up being just as long:</p>
1690 </div>
1696 represents an element that is the first child of some other element.
1710 fragment:
1718 a:first-child /* Same (assuming a is not the root element) */</pre>
1719 </div>
1724 represents an element that is the last child of some other element.
1731 </div>
1736 represents an element that is the first sibling of its type in the list of
1737 children of its parent element.
1741 <p>The following selector represents a definition title
1744 its parent element.</p>
1747 elements in the following example but not for the third one:</p>
1759 </div>
1765 the last sibling of its type in the list of children of its parent
1766 element.</p>
1770 <p>The following selector represents the last data cell
1773 </div>
1777 <p>Represents an element that has a parent element and whose parent
1778 element has no other element children. Same as
1781 specificity.</p>
1785 <p>Represents an element that has a parent element and whose parent
1786 element has no other element children with the same element name. Same
1789 specificity.</p>
1795 no children at all. In terms of the DOM, only element nodes and text
1796 nodes (including CDATA nodes and entity references) whose data has a
1797 non-zero length must be considered as affecting emptiness; comments,
1798 PIs, and other nodes must not affect whether an element is considered
1799 empty or not.</p>
1806 following fragments:</p>
1810 </div>
1812 <h4><a name=content-selectors>6.6.6. Blank</a></h4> <!-- It's the Return of Appendix H!!! Run away! -->
1815 <!-- (used to be :contains()) -->
1821 selector</a> (excluding the negation pseudo-class itself and
1822 pseudo-elements) as an argument. It represents an element that is not
1823 represented by the argument.
1825 <!-- pseudo-elements are not simple selectors, so the above paragraph
1826 may be a bit confusing -->
1831 elements in an HTML document that are not disabled.</p>
1834 elements.</p>
1836 <p>The following group of selectors represents all HTML elements
1837 except links.</p>
1839 </div>
1841 <p>Default namespace declarations do not affect the argument of the
1842 negation pseudo-class unless the argument is a universal selector or a
1843 type selector.</p>
1847 <p>Assuming that the default namespace is bound to
1848 "http://example.com/", the following selector represents all
1849 elements that are not in that namespace:</p>
1851 <p>The following CSS selector matches any element being hovered,
1852 regardless of its namespace. In particular, it is not limited to
1853 only matching elements in the default namespace that are not being
1854 hovered, and elements not in the default namespace don't match the
1857 </div>
1863 specificity.</p>
1867 <p>Pseudo-elements create abstractions about the document tree beyond
1868 those specified by the document language. For instance, document
1869 languages do not offer mechanisms to access the first letter or first
1870 line of an element's content. Pseudo-elements allow designers to refer
1871 to this otherwise inaccessible information. Pseudo-elements may also
1872 provide designers a way to refer to content that does not exist in the
1875 content).</p>
1878 by the name of the pseudo-element.</p>
1881 in order to establish a discrimination between pseudo-classes and
1882 pseudo-elements. For compatibility with existing style sheets, user
1883 agents must also accept the previous one-colon notation for
1889 <p>Only one pseudo-element may appear per selector, and if present it
1890 must appear after the sequence of simple selectors that represents the
1892 future version of this specification may allow multiple
1893 pesudo-elements per selector.</span></p>
1898 of the first formatted line of an element.
1905 </div>
1908 HTML element. It does match a pseudo-element that conforming user
1909 agents will insert at the beginning of every paragraph.</p>
1911 <p>Note that the length of the first line depends on a number of
1912 factors, including the width of the page, the font size, etc. Thus,
1913 an ordinary HTML paragraph such as:</p>
1915 <pre>
1917 paragraph that will be broken into several
1918 lines. The first line will be identified
1919 by a fictional tag sequence. The other lines
1920 will be treated as ordinary lines in the
1922 </pre>
1924 <p>the lines of which happen to be broken as follows:
1926 <pre>
1927 THIS IS A SOMEWHAT LONG HTML PARAGRAPH THAT
1928 will be broken into several lines. The first
1929 line will be identified by a fictional tag
1930 sequence. The other lines will be treated as
1931 ordinary lines in the paragraph.
1932 </pre>
1936 fictional tag sequence helps to show how properties are inherited.</p>
1938 <pre>
1941 lines. The first line will be identified
1942 by a fictional tag sequence. The other lines
1943 will be treated as ordinary lines in the
1945 </pre>
1947 <p>If a pseudo-element breaks up a real element, the desired effect
1948 can often be described by a fictional tag sequence that closes and
1949 then re-opens the element. Thus, if we mark up the previous paragraph
1952 <pre>
1954 paragraph that will be broken into several
1956 by a fictional tag sequence. The other lines
1957 will be treated as ordinary lines in the
1959 </pre>
1961 <p>the user agent could simulate start and end tags for
1965 <pre>
1967 somewhat long HTML
1968 paragraph that will <b></SPAN></b></P::first-line><b><SPAN class="test"></b> be
1969 broken into several
1971 by a fictional tag sequence. The other lines
1972 will be treated as ordinary lines in the
1974 </pre>
1977 attached to a block-level element, an inline-block, a table-caption,
1978 or a table-cell.</p>
1981 element may occur inside a
1982 block-level descendant in the same flow (i.e., a block-level
1983 descendant that is not positioned and not a float). E.g., the first
1988 <p>The first line of a table-cell or inline-block cannot be the first
1999 <p>A UA should act as if the fictional start tags of the
2001 innermost enclosing block-level element. (Since CSS1 and CSS2 were
2002 silent on this case, authors should not rely on this behavior.) Here
2003 is an example. The fictional tag sequence for</p>
2005 <pre>
2010 </pre>
2014 <pre>
2016 <P><DIV::first-line><P::first-line>First paragraph</P::first-line></DIV::first-line></P>
2019 </pre>
2022 inline-level element, but with certain restrictions. In CSS, the
2024 pseudo-element: font properties, color property, background
2025 properties, 'word-spacing', 'letter-spacing', 'text-decoration',
2026 'vertical-align', 'text-transform', 'line-height'. UAs may apply other
2027 properties as well.</p>
2033 letter of the first line of a block, if it is not preceded by any
2034 other content (such as images or inline tables) on its line. The
2036 caps", which are common typographical effects. This type of initial
2037 letter is similar to an inline-level element if its 'float' property
2038 is 'none'; otherwise, it is similar to a floated element.</p>
2041 pseudo-elements: font properties, 'text-decoration', 'text-transform',
2042 'letter-spacing', 'word-spacing' (when appropriate), 'line-height',
2043 'float', 'vertical-align' (only if 'float' is 'none'), margin
2044 properties, padding properties, border properties, color property,
2045 background properties. UAs may apply other properties as well. To
2046 allow UAs to render a typographically correct drop cap or initial cap,
2047 the UA may choose a line-height, width and height based on the shape
2048 of the letter, unlike for normal elements.</p>
2052 <p>This example shows a possible rendering of an initial cap. Note
2054 pseudo-element is 1.1, but the UA in this example has computed the
2055 height of the first letter differently, so that it doesn't cause any
2056 unnecessary space between the first two lines. Also note that the
2059 <pre>
2060 p { line-height: 1.1 }
2061 p::first-letter { font-size: 3em; font-weight: normal }
2062 span { font-weight: bold }
2063 ...
2067 En dagelix geschrey de bange stad ontzet.
2068 </pre>
2071 </div>
2072 </div>
2077 <pre>
2084 P::first-letter { font-size: 200%; font-weight: bold; float: left }
2085 SPAN { text-transform: uppercase }
2093 </pre>
2098 <P><img src="first-letter.gif" alt="Image illustrating the combined effect of the ::first-letter and ::first-line pseudo-elements"></p>
2099 </div>
2104 <pre>
2108 T
2111 few words of an article in the Economist.
2113 </pre>
2116 the content (i.e., the initial character), while the ::first-line
2117 pseudo-element start tag is inserted right after the start tag of the
2118 block element.</p> </div>
2120 <p>In order to achieve traditional drop caps formatting, user agents
2121 may approximate font sizes, for example to align baselines. Also, the
2122 glyph outline may be taken into account when formatting.</p>
2126 punctuation classes), that precedes or follows the first letter should
2132 </div>
2139 block, list-item, table-cell, table-caption, and inline-block
2141 may allow this pesudo-element to apply to more element
2142 types.</span></p>
2145 such elements that contain text, or that have a descendant in the same
2146 flow that contains text. A UA should act as if the fictional start tag
2147 of the ::first-letter pseudo-element is just before the first text of
2148 the element, even if that first text is in a descendant.</p>
2152 <p>The fictional tag sequence for this HTMLfragment:
2155 <p>is:
2158 </div>
2160 <p>The first letter of a table-cell or inline-block cannot be the
2173 <p>In CSS, if an element is a list item ('display: list-item'), the
2175 principal box after the marker. UAs may ignore
2185 </div>
2187 <p>Some languages may have specific rules about how to treat certain
2188 letter combinations. In Dutch, for example, if the letter combination
2189 "ij" appears at the beginning of a word, both letters should be
2192 <p>If the letters that would form the ::first-letter are not in the
2194 may create a ::first-letter pseudo-element from one of the elements,
2195 both elements, or simply not create a pseudo-element.</p>
2197 <p>Similarly, if the first letter(s) of the block are not at the start
2198 of the line (for example due to bidirectional reordering), then the UA
2199 need not create the pseudo-element(s).
2204 how overlapping pseudo-elements may interact. The first letter of
2205 each P element will be green with a font size of '24pt'. The rest of
2206 the first formatted line will be 'blue' while the rest of the
2207 paragraph will be 'red'.</p>
2210 p::first-letter { color: green; font-size: 200% }
2211 p::first-line { color: blue }
2222 S
2225 ends up on two lines
2232 </div>
2238 of a document that has been highlighted by the user. This also
2239 applies, for example, to selected text within an editable text
2240 field. This pseudo-element should not be confused with the <code><a
2245 nature, and is altered by user action, it is reasonable to expect that
2246 when a UA re-renders to a static medium (such as a printed page, see
2248 dynamic medium (like screen), the UA may wish to transfer the current
2250 appropriate formatting and rendering take effect as well. This is not
2252 pseudo-element for static media.
2255 pseudo-elements: color, background, cursor (optional), outline
2256 (optional). The computed value of the 'background-image' property on
2263 can be used to describe generated content before or after an element's
2270 element including the inserted text.</p>
2276 <p>At times, authors may want selectors to describe an element that is
2277 the descendant of another element in the document tree (e.g., "an
2278 <code>EM</code> element that is contained within an <code>H1</code>
2279 element"). Descendant combinators express such a relationship. A
2281 separates two sequences of simple selectors. A selector of the form
2291 description of the following fragment:</p>
2298 either side of the "*" is not part of the universal selector; the
2299 whitespace is a combinator indicating that the DIV must be the
2300 ancestor of some element, and that that element must be an ancestor
2301 of the P.</p>
2302 <p>The following selector, which combines descendant combinators and
2307 </div>
2312 between two elements. A child combinator is made of the
2314 separates two sequences of simple selectors.
2322 <p>The following example combines descendant combinators and child
2323 combinators.</p>
2330 </div>
2332 <p>For information on selecting the first child of an element, please
2333 see the section on the <code><a
2335 above.</p>
2339 <p>There are two different sibling combinators: the adjacent sibling
2340 combinator and the general sibling combinator. In both cases,
2341 non-element nodes (e.g. text between elements) are ignored when
2342 considering adjacency of elements.</p>
2348 sequences of simple selectors. The elements represented by the two
2349 sequences share the same parent in the document tree and the element
2350 represented by the first sequence immediately precedes the element
2351 represented by the second one.</p>
2358 <p>The following selector is conceptually similar to the one in the
2359 previous example, except that it adds an attribute selector — it
2363 </div>
2370 simple selectors. The elements represented by the two sequences share
2371 the same parent in the document tree and the element represented by
2372 the first sequence precedes (not necessarily immediately) the element
2373 represented by the second one.</p>
2379 is a correct and valid, but partial, description of:</p>
2383 </div>
2389 <ul>
2391 <li>count the number of class selectors, attributes selectors, and pseudo-classes in the selector (= b)</li>
2394 </ul>
2397 are counted like any other, but the negation itself does not count as
2398 a pseudo-class.</p>
2400 <p>Concatenating the three numbers a-b-c (in a number system with a
2401 large base) gives the specificity.</p>
2414 </pre>
2415 </div>
2425 <p>The grammar below defines the syntax of Selectors. It is globally
2427 it directly, since it doesn't express the parsing conventions). The
2428 format of the productions is optimized for human consumption and some
2430 are used:</p>
2432 <ul>
2438 </ul>
2442 <pre>selectors_group
2443 : selector [ COMMA S* selector ]*
2444 ;
2446 selector
2447 : simple_selector_sequence [ combinator simple_selector_sequence ]*
2448 ;
2450 combinator
2451 /* combinators can be surrounded by white space */
2452 : PLUS S* | GREATER S* | TILDE S* | S+
2453 ;
2455 simple_selector_sequence
2456 : [ type_selector | universal ]
2457 [ HASH | class | attrib | pseudo | negation ]*
2458 | [ HASH | class | attrib | pseudo | negation ]+
2459 ;
2461 type_selector
2462 : [ namespace_prefix ]? element_name
2463 ;
2465 namespace_prefix
2466 : [ IDENT | '*' ]? '|'
2467 ;
2469 element_name
2470 : IDENT
2471 ;
2473 universal
2474 : [ namespace_prefix ]? '*'
2475 ;
2477 class
2478 : '.' IDENT
2479 ;
2481 attrib
2482 : '[' S* [ namespace_prefix ]? IDENT S*
2483 [ [ PREFIXMATCH |
2484 SUFFIXMATCH |
2485 SUBSTRINGMATCH |
2486 '=' |
2487 INCLUDES |
2488 DASHMATCH ] S* [ IDENT | STRING ] S*
2489 ]? ']'
2490 ;
2492 pseudo
2493 /* '::' starts a pseudo-element, ':' a pseudo-class */
2494 /* Exceptions: :first-line, :first-letter, :before and :after. */
2495 /* Note that pseudo-elements are restricted to one per selector and */
2496 /* occur only in the last simple_selector_sequence. */
2497 : ':' ':'? [ IDENT | functional_pseudo ]
2498 ;
2500 functional_pseudo
2501 : FUNCTION S* expression ')'
2502 ;
2504 expression
2505 /* In CSS3, the expressions are identifiers, strings, */
2506 /* or of the form "an+b" */
2507 : [ [ PLUS | '-' | DIMENSION | NUMBER | STRING | IDENT ] S* ]+
2508 ;
2510 negation
2511 : NOT S* negation_arg S* ')'
2512 ;
2514 negation_arg
2515 : type_selector | universal | HASH | class | attrib | pseudo
2516 ;</pre>
2523 case-insensitive.</p>
2526 number that current versions of Flex can deal with (decimal 255). They
2531 <pre>%option case-insensitive
2533 ident [-]?{nmstart}{nmchar}*
2534 name {nmchar}+
2535 nmstart [_a-z]|{nonascii}|{escape}
2538 escape {unicode}|\\[^\n\r\f0-9a-f]
2539 nmchar [_a-z0-9-]|{nonascii}|{escape}
2541 string {string1}|{string2}
2543 string2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*\'
2544 invalid {invalid1}|{invalid2}
2546 invalid2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*
2547 nl \n|\r\n|\r|\f
2548 w [ \t\r\n\f]*
2550 %%
2552 [ \t\r\n\f]+ return S;
2559 {ident} return IDENT;
2560 {string} return STRING;
2562 {num} return NUMBER;
2569 @{ident} return ATKEYWORD;
2570 {invalid} return INVALID;
2571 {num}% return PERCENTAGE;
2572 {num}{ident} return DIMENSION;
2578 U\+[0-9a-f?]{1,6}(-[0-9a-f]{1,6})? return UNICODE_RANGE;
2580 \/\*[^*]*\*+([^/*][^*]*\*+)*\/ /* ignore comments */
2582 . return *yytext;</pre>
2586 <h2><a name=downlevel>11. Namespaces and down-level clients</a></h2>
2588 <p>An important issue is the interaction of CSS selectors with XML
2589 documents in web clients that were produced prior to this
2590 document. Unfortunately, due to the fact that namespaces must be
2591 matched based on the URI which identifies the namespace, not the
2592 namespace prefix, some mechanism is required to identify namespaces in
2593 CSS by their URI as well. Without such a mechanism, it is impossible
2594 to construct a CSS style sheet which will properly match selectors in
2595 all cases against a random set of XML documents. However, given
2596 complete knowledge of the XML document to which a style sheet is to be
2597 applied, and a limited use of namespaces within the XML document, it
2598 is possible to construct a style sheet in which selectors would match
2599 elements and attributes correctly.</p>
2601 <p>It should be noted that a down-level CSS client will (if it
2602 properly conforms to CSS forward compatible parsing rules) ignore all
2603 <code>@namespace</code> at-rules, as well as all style rules that make
2604 use of namespace qualified element type or attribute selectors. The
2605 syntax of delimiting namespace prefixes in CSS was deliberately chosen
2606 so that down-level CSS clients would ignore the style rules rather
2607 than possibly match them incorrectly.</p>
2609 <p>The use of default namespaces in CSS makes it possible to write
2610 element type selectors that will function in both namespace aware CSS
2611 clients as well as down-level clients. It should be noted that
2612 down-level clients may incorrectly match selectors against XML
2613 elements in other namespaces.</p>
2615 <p>The following are scenarios and examples in which it is possible to
2616 construct style sheets which would function properly in web clients
2617 that do not implement this proposal.</p>
2619 <ol>
2620 <li>
2622 <p>The XML document does not use namespaces.</p>
2624 <ul>
2626 <li>In this case, it is obviously not necessary to declare or use
2627 namespaces in the style sheet. Standard CSS element type and
2628 attribute selectors will function adequately in a down-level
2629 client.</li>
2631 <li>In a CSS namespace aware client, the default behavior of
2632 element selectors matching without regard to namespace will
2633 function properly against all elements, since no namespaces are
2634 present. However, the use of specific element type selectors that
2636 will guarantee that selectors will match only XML elements that do
2637 not have a declared namespace. </li>
2639 </ul>
2641 </li>
2643 <li>
2645 <p>The XML document defines a single, default namespace used
2646 throughout the document. No namespace prefixes are used in element
2647 names.</p>
2649 <ul>
2651 <li>In this case, a down-level client will function as if
2652 namespaces were not used in the XML document at all. Standard CSS
2653 element type and attribute selectors will match against all
2654 elements. </li>
2656 </ul>
2658 </li>
2660 <li>
2662 <p>The XML document does <b>not</b> use a default namespace, all
2663 namespace prefixes used are known to the style sheet author, and
2664 there is a direct mapping between namespace prefixes and namespace
2665 URIs. (A given prefix may only be mapped to one namespace URI
2666 throughout the XML document; there may be multiple prefixes mapped
2667 to the same URI).</p>
2669 <ul>
2671 <li>In this case, the down-level client will view and match
2672 element type and attribute selectors based on their fully
2673 qualified name, not the local part as outlined in the <a
2676 to describe the fully qualified names, e.g.
2678 <code><html:h1></code>. Selectors using the qualified name
2679 will only match XML elements that use the same prefix. Other
2680 namespace prefixes used in the XML that are mapped to the same URI
2681 will not match as expected unless additional CSS style rules are
2682 declared for them.</li>
2684 <li>Note that selectors declared in this fashion will
2685 <em>only</em> match in down-level clients. A CSS namespace aware
2686 client will match element type and attribute selectors based on
2687 the name's local part. Selectors declared with the fully
2688 qualified name will not match (unless there is no namespace prefix
2689 in the fully qualified name).</li>
2691 </ul>
2693 </li>
2695 </ol>
2697 <p>In other scenarios: when the namespace prefixes used in the XML are
2698 not known in advance by the style sheet author; or a combination of
2699 elements with no namespace are used in conjunction with elements using
2700 a default namespace; or the same namespace prefix is mapped to
2701 <em>different</em> namespace URIs within the same document, or in
2702 different documents; it is impossible to construct a CSS style sheet
2703 that will function properly against all elements in those documents,
2704 unless, the style sheet is written using a namespace URI syntax (as
2705 outlined in this document or similar) and the document is processed by
2706 a CSS and XML namespace aware client.</p>
2708 <h2><a name=profiling>12. Profiles</a></h2>
2710 <p>Each specification using Selectors must define the subset of W3C
2711 Selectors it allows and excludes, and describe the local meaning of
2712 all the components of that subset.</p>
2714 <p>Non normative examples:
2718 <tbody>
2719 <tr>
2721 <tr>
2722 <th>Specification</th>
2723 <td>CSS level 1</td></tr>
2724 <tr>
2725 <th>Accepts</th>
2726 <td>type selectors<br>class selectors<br>ID selectors<br>:link,
2727 :visited and :active pseudo-classes<br>descendant combinator
2728 <br>::first-line and ::first-letter pseudo-elements</td></tr>
2729 <tr>
2730 <th>Excludes</th>
2731 <td>
2733 <p>universal selector<br>attribute selectors<br>:hover and :focus
2734 pseudo-classes<br>:target pseudo-class<br>:lang() pseudo-class<br>all UI
2735 element states pseudo-classes<br>all structural
2736 pseudo-classes<br>negation pseudo-class<br>all
2737 UI element fragments pseudo-elements<br>::before and ::after
2738 pseudo-elements<br>child combinators<br>sibling combinators
2740 <p>namespaces</td></tr>
2741 <tr>
2742 <th>Extra constraints</th>
2743 <td>only one class selector allowed per sequence of simple
2744 selectors</td></tr></tbody></table><br><br>
2746 <tbody>
2747 <tr>
2749 <tr>
2750 <th>Specification</th>
2751 <td>CSS level 2</td></tr>
2752 <tr>
2753 <th>Accepts</th>
2754 <td>type selectors<br>universal selector<br>attribute presence and
2755 values selectors<br>class selectors<br>ID selectors<br>:link, :visited,
2756 :active, :hover, :focus, :lang() and :first-child pseudo-classes
2757 <br>descendant combinator<br>child combinator<br>adjacent sibling
2758 combinator<br>::first-line and ::first-letter pseudo-elements<br>::before
2759 and ::after pseudo-elements</td></tr>
2760 <tr>
2761 <th>Excludes</th>
2762 <td>
2764 <p>content selectors<br>substring matching attribute
2765 selectors<br>:target pseudo-classes<br>all UI element
2766 states pseudo-classes<br>all structural pseudo-classes other
2767 than :first-child<br>negation pseudo-class<br>all UI element
2768 fragments pseudo-elements<br>general sibling combinators
2770 <p>namespaces</td></tr>
2771 <tr>
2772 <th>Extra constraints</th>
2773 <td>more than one class selector per sequence of simple selectors (CSS1
2774 constraint) allowed</td></tr></tbody></table>
2776 <p>In CSS, selectors express pattern matching rules that determine which style
2777 rules apply to elements in the document tree.
2779 <p>The following selector (CSS level 2) will <b>match</b> all anchors <code>a</code>
2780 with attribute <code>name</code> set inside a section 1 header <code>h1</code>:
2781 <pre>h1 a[name]</pre>
2783 <p>All CSS declarations attached to such a selector are applied to elements
2784 matching it. </div>
2788 <tbody>
2789 <tr>
2791 <tr>
2792 <th>Specification</th>
2793 <td>STTS 3</td>
2794 </tr>
2795 <tr>
2796 <th>Accepts</th>
2797 <td>
2799 <p>type selectors<br>universal selectors<br>attribute selectors<br>class
2800 selectors<br>ID selectors<br>all structural pseudo-classes<br>
2801 all combinators
2803 <p>namespaces</td></tr>
2804 <tr>
2805 <th>Excludes</th>
2806 <td>non-accepted pseudo-classes<br>pseudo-elements<br></td></tr>
2807 <tr>
2808 <th>Extra constraints</th>
2809 <td>some selectors and combinators are not allowed in fragment
2810 descriptions on the right side of STTS declarations.</td></tr></tbody></table>
2811 <form>
2837 </form>
2839 <p>Selectors can be used in STTS 3 in two different
2840 manners:
2841 <ol>
2842 <li>a selection mechanism equivalent to CSS selection mechanism: declarations
2843 attached to a given selector are applied to elements matching that selector,
2844 <li>fragment descriptions that appear on the right side of declarations.
2845 </li></ol></div>
2847 <h2><a name=Conformance></a>13. Conformance and requirements</h2>
2849 <p>This section defines conformance with the present specification only.
2851 <p>The inability of a user agent to implement part of this specification due to
2852 the limitations of a particular device (e.g., non interactive user agents will
2853 probably not implement dynamic pseudo-classes because they make no sense without
2854 interactivity) does not imply non-conformance.
2856 <p>All specifications reusing Selectors must contain a <a
2858 subset of Selectors it accepts or excludes, and describing the constraints
2859 it adds to the current specification.
2861 <p>Invalidity is caused by a parsing error, e.g. an unrecognized token or a token
2862 which is not allowed at the current parsing point.
2864 <p>User agents must observe the rules for handling parsing errors:
2865 <ul>
2866 <li>a simple selector containing an undeclared namespace prefix is invalid</li>
2867 <li>a selector containing an invalid simple selector, an invalid combinator
2868 or an invalid token is invalid. </li>
2869 <li>a group of selectors containing an invalid selector is invalid.</li>
2870 </ul>
2873 errors. (In the case of CSS, the entire rule in which the selector is
2874 used is dropped.)</p>
2876 <!-- Apparently all these references are out of date:
2877 <p>Implementations of this specification must behave as
2879 when parsing selectors and attempting matches. (In particular,
2880 implementations must assume the data is normalized and must not
2881 normalize it.) Normative rules for matching strings are defined in
2884 specification.</p>-->
2886 <h2><a name=Tests></a>14. Tests</h2>
2888 <p>This specification has <a
2890 suite</a> allowing user agents to verify their basic conformance to
2891 the specification. This test suite does not pretend to be exhaustive
2892 and does not cover all possible combined cases of Selectors.</p>
2894 <h2><a name=ACKS></a>15. Acknowledgements</h2>
2896 <p>The CSS working group would like to thank everyone who has sent
2897 comments on this specification over the years.</p>
2899 <p>The working group would like to extend special thanks to Donna
2900 McManus, Justin Baker, Joel Sklar, and Molly Ives Brower who perfermed
2901 the final editorial review.</p>
2903 <h2><a name=references>16. References</a></h2>
2907 <dt>[CSS1]
2908 <dd><a name=refsCSS1></a> Bert Bos, Håkon Wium Lie; "<cite>Cascading Style Sheets, level 1</cite>", W3C Recommendation, 17 Dec 1996, revised 11 Jan 1999
2911 <dt>[CSS21]
2912 <dd><a name=refsCSS21></a> Bert Bos, Tantek Çelik, Ian Hickson, Håkon Wium Lie, editors; "<cite>Cascading Style Sheets, level 2 revision 1</cite>", W3C Working Draft, 13 June 2005
2915 <dt>[CWWW]
2916 <dd><a name=refsCWWW></a> Martin J. Dürst, François Yergeau, Misha Wolf, Asmus Freytag, Tex Texin, editors; "<cite>Character Model for the World Wide Web</cite>", W3C Recommendation, 15 February 2005
2919 <dt>[FLEX]
2920 <dd><a name="refsFLEX"></a> "<cite>Flex: The Lexical Scanner Generator</cite>", Version 2.3.7, ISBN 1882114213
2922 <dt>[HTML4]
2923 <dd><a name="refsHTML4"></a> Dave Ragget, Arnaud Le Hors, Ian Jacobs, editors; "<cite>HTML 4.01 Specification</cite>", W3C Recommendation, 24 December 1999
2926 <dt>[MATH]
2927 <dd><a name="refsMATH"></a> Patrick Ion, Robert Miner, editors; "<cite>Mathematical Markup Language (MathML) 1.01</cite>", W3C Recommendation, revision of 7 July 1999
2928 <dd>(<code><a href="http://www.w3.org/TR/REC-MathML/">http://www.w3.org/TR/REC-MathML/</a></code>)
2930 <dt>[RFC3066]
2931 <dd><a name="refsRFC3066"></a> H. Alvestrand; "<cite>Tags for the Identification of Languages</cite>", Request for Comments 3066, January 2001
2932 <dd>(<a href="http://www.ietf.org/rfc/rfc3066.txt"><code>http://www.ietf.org/rfc/rfc3066.txt</code></a>)
2934 <dt>[STTS]
2935 <dd><a name=refsSTTS></a> Daniel Glazman; "<cite>Simple Tree Transformation Sheets 3</cite>", Electricité de France, submission to the W3C, 11 November 1998
2936 <dd>(<code><a href="http://www.w3.org/TR/NOTE-STTS3">http://www.w3.org/TR/NOTE-STTS3</a></code>)
2938 <dt>[SVG]
2939 <dd><a name="refsSVG"></a> Jon Ferraiolo, 藤沢 淳, Dean Jackson, editors; "<cite>Scalable Vector Graphics (SVG) 1.1 Specification</cite>", W3C Recommendation, 14 January 2003
2942 <dt>[UNICODE]</dt>
2944 href="http://www.unicode.org/versions/Unicode4.1.0/">The Unicode Standard, Version 4.1</a></cite>, The Unicode Consortium. Boston, MA, Addison-Wesley, March 2005. ISBN 0-321-18578-1, as amended by <a href="http://www.unicode.org/versions/Unicode4.0.1/">Unicode 4.0.1</a> and <a href="http://www.unicode.org/versions/Unicode4.1.0/">Unicode 4.1.0</a>.
2945 <dd>(<code><a href="http://www.unicode.org/versions/">http://www.unicode.org/versions/</a></code>)</dd>
2947 <dt>[XML10]
2948 <dd><a name="refsXML10"></a> Tim Bray, Jean Paoli, C. M. Sperberg-McQueen, Eve Maler, François Yergeau, editors; "<cite>Extensible Markup Language (XML) 1.0 (Third Edition)</cite>", W3C Recommendation, 4 February 2004
2951 <dt>[XMLNAMES]
2952 <dd><a name="refsXMLNAMES"></a> Tim Bray, Dave Hollander, Andrew Layman, editors; "<cite>Namespaces in XML</cite>", W3C Recommendation, 14 January 1999
2953 <dd>(<a href="http://www.w3.org/TR/REC-xml-names/"><code>http://www.w3.org/TR/REC-xml-names/</code></a>)
2955 <dt>[YACC]
2956 <dd><a name="refsYACC"></a> S. C. Johnson; "<cite>YACC — Yet another compiler compiler</cite>", Technical Report, Murray Hill, 1975
2958 </dl>
2959 </body>
2960 </html>