Annotation of html5/spec/the-link-element.html, revision 1.178
1.88 mike 1: <!DOCTYPE html>
1.159 sruby 2: <html lang="en-US-x-Hixie"><head><title>4.2.4 The link element — HTML5</title><style type="text/css">
1.1 mike 3: pre { margin-left: 2em; white-space: pre-wrap; }
4: h2 { margin: 3em 0 1em 0; }
5: h3 { margin: 2.5em 0 1em 0; }
6: h4 { margin: 2.5em 0 0.75em 0; }
7: h5, h6 { margin: 2.5em 0 1em; }
8: h1 + h2, h1 + h2 + h2 { margin: 0.75em 0 0.75em; }
9: h2 + h3, h3 + h4, h4 + h5, h5 + h6 { margin-top: 0.5em; }
10: p { margin: 1em 0; }
11: hr:not(.top) { display: block; background: none; border: none; padding: 0; margin: 2em 0; height: auto; }
12: dl, dd { margin-top: 0; margin-bottom: 0; }
13: dt { margin-top: 0.75em; margin-bottom: 0.25em; clear: left; }
14: dt + dt { margin-top: 0; }
15: dd dt { margin-top: 0.25em; margin-bottom: 0; }
16: dd p { margin-top: 0; }
17: dd dl + p { margin-top: 1em; }
18: dd table + p { margin-top: 1em; }
19: p + * > li, dd li { margin: 1em 0; }
20: dt, dfn { font-weight: bold; font-style: normal; }
21: i, em { font-style: italic; }
22: dt dfn { font-style: italic; }
23: pre, code { font-size: inherit; font-family: monospace; font-variant: normal; }
24: pre strong { color: black; font: inherit; font-weight: bold; background: yellow; }
25: pre em { font-weight: bolder; font-style: normal; }
26: @media screen { code { color: orangered; } code :link, code :visited { color: inherit; } }
27: var sub { vertical-align: bottom; font-size: smaller; position: relative; top: 0.1em; }
28: table { border-collapse: collapse; border-style: hidden hidden none hidden; }
29: table thead, table tbody { border-bottom: solid; }
30: table tbody th:first-child { border-left: solid; }
31: table tbody th { text-align: left; }
32: table td, table th { border-left: solid; border-right: solid; border-bottom: solid thin; vertical-align: top; padding: 0.2em; }
33: blockquote { margin: 0 0 0 2em; border: 0; padding: 0; font-style: italic; }
34:
35: .bad, .bad *:not(.XXX) { color: gray; border-color: gray; background: transparent; }
36: .matrix, .matrix td { border: none; text-align: right; }
37: .matrix { margin-left: 2em; }
38: .dice-example { border-collapse: collapse; border-style: hidden solid solid hidden; border-width: thin; margin-left: 3em; }
39: .dice-example caption { width: 30em; font-size: smaller; font-style: italic; padding: 0.75em 0; text-align: left; }
40: .dice-example td, .dice-example th { border: solid thin; width: 1.35em; height: 1.05em; text-align: center; padding: 0; }
41:
42: .toc dfn, h1 dfn, h2 dfn, h3 dfn, h4 dfn, h5 dfn, h6 dfn { font: inherit; }
43: img.extra, p.overview { float: right; }
44: pre.idl { border: solid thin; background: #EEEEEE; color: black; padding: 0.5em 1em; position: relative; }
45: pre.idl :link, pre.idl :visited { color: inherit; background: transparent; }
46: pre.idl::before { content: "IDL"; font: bold small sans-serif; padding: 0.5em; background: white; position: absolute; top: 0; margin: -1px 0 0 -4em; width: 1.5em; border: thin solid; border-radius: 0 0 0 0.5em }
47: pre.css { border: solid thin; background: #FFFFEE; color: black; padding: 0.5em 1em; }
48: pre.css:first-line { color: #AAAA50; }
49: dl.domintro { color: green; margin: 2em 0 2em 2em; padding: 0.5em 1em; border: none; background: #DDFFDD; }
50: hr + dl.domintro, div.impl + dl.domintro { margin-top: 2.5em; margin-bottom: 1.5em; }
51: dl.domintro dt, dl.domintro dt * { color: black; text-decoration: none; }
52: dl.domintro dd { margin: 0.5em 0 1em 2em; padding: 0; }
53: dl.domintro dd p { margin: 0.5em 0; }
54: dl.domintro:before { display: table; margin: -1em -0.5em -0.5em auto; width: auto; content: 'This box is non-normative. Implementation requirements are given below this box.'; color: black; font-style: italic; border: solid 2px; background: white; padding: 0 0.25em; }
55: dl.switch { padding-left: 2em; }
56: dl.switch > dt { text-indent: -1.5em; }
57: dl.switch > dt:before { content: '\21AA'; padding: 0 0.5em 0 0; display: inline-block; width: 1em; text-align: right; line-height: 0.5em; }
58: dl.triple { padding: 0 0 0 1em; }
59: dl.triple dt, dl.triple dd { margin: 0; display: inline }
60: dl.triple dt:after { content: ':'; }
61: dl.triple dd:after { content: '\A'; white-space: pre; }
62: .diff-old { text-decoration: line-through; color: silver; background: transparent; }
63: .diff-chg, .diff-new { text-decoration: underline; color: green; background: transparent; }
64: a .diff-new { border-bottom: 1px blue solid; }
65:
66: h2 { page-break-before: always; }
67: h1, h2, h3, h4, h5, h6 { page-break-after: avoid; }
68: h1 + h2, hr + h2.no-toc { page-break-before: auto; }
69:
70: p > span:not([title=""]):not([class="XXX"]):not([class="impl"]):not([class="note"]),
71: li > span:not([title=""]):not([class="XXX"]):not([class="impl"]):not([class="note"]), { border-bottom: solid #9999CC; }
72:
73: div.head { margin: 0 0 1em; padding: 1em 0 0 0; }
74: div.head p { margin: 0; }
75: div.head h1 { margin: 0; }
76: div.head .logo { float: right; margin: 0 1em; }
77: div.head .logo img { border: none } /* remove border from top image */
78: div.head dl { margin: 1em 0; }
79: div.head p.copyright, div.head p.alt { font-size: x-small; font-style: oblique; margin: 0; }
80:
81: body > .toc > li { margin-top: 1em; margin-bottom: 1em; }
82: body > .toc.brief > li { margin-top: 0.35em; margin-bottom: 0.35em; }
83: body > .toc > li > * { margin-bottom: 0.5em; }
84: body > .toc > li > * > li > * { margin-bottom: 0.25em; }
85: .toc, .toc li { list-style: none; }
86:
87: .brief { margin-top: 1em; margin-bottom: 1em; line-height: 1.1; }
88: .brief li { margin: 0; padding: 0; }
89: .brief li p { margin: 0; padding: 0; }
90:
91: .category-list { margin-top: -0.75em; margin-bottom: 1em; line-height: 1.5; }
92: .category-list::before { content: '\21D2\A0'; font-size: 1.2em; font-weight: 900; }
93: .category-list li { display: inline; }
94: .category-list li:not(:last-child)::after { content: ', '; }
95: .category-list li > span, .category-list li > a { text-transform: lowercase; }
96: .category-list li * { text-transform: none; } /* don't affect <code> nested in <a> */
97:
98: .XXX { color: #E50000; background: white; border: solid red; padding: 0.5em; margin: 1em 0; }
99: .XXX > :first-child { margin-top: 0; }
100: p .XXX { line-height: 3em; }
101: .annotation { border: solid thin black; background: #0C479D; color: white; position: relative; margin: 8px 0 20px 0; }
102: .annotation:before { position: absolute; left: 0; top: 0; width: 100%; height: 100%; margin: 6px -6px -6px 6px; background: #333333; z-index: -1; content: ''; }
103: .annotation :link, .annotation :visited { color: inherit; }
104: .annotation :link:hover, .annotation :visited:hover { background: transparent; }
105: .annotation span { border: none ! important; }
106: .note { color: green; background: transparent; font-family: sans-serif; }
107: .warning { color: red; background: transparent; }
108: .note, .warning { font-weight: bolder; font-style: italic; }
109: .note em, .warning em, .note i, .warning i { font-style: normal; }
110: p.note, div.note { padding: 0.5em 2em; }
111: span.note { padding: 0 2em; }
112: .note p:first-child, .warning p:first-child { margin-top: 0; }
113: .note p:last-child, .warning p:last-child { margin-bottom: 0; }
114: .warning:before { font-style: normal; }
115: p.note:before { content: 'Note: '; }
116: p.warning:before { content: '\26A0 Warning! '; }
117:
118: .bookkeeping:before { display: block; content: 'Bookkeeping details'; font-weight: bolder; font-style: italic; }
119: .bookkeeping { font-size: 0.8em; margin: 2em 0; }
120: .bookkeeping p { margin: 0.5em 2em; display: list-item; list-style: square; }
121: .bookkeeping dt { margin: 0.5em 2em 0; }
122: .bookkeeping dd { margin: 0 3em 0.5em; }
123:
124: h4 { position: relative; z-index: 3; }
125: h4 + .element, h4 + div + .element { margin-top: -2.5em; padding-top: 2em; }
126: .element {
127: background: #EEEEFF;
128: color: black;
129: margin: 0 0 1em 0.15em;
130: padding: 0 1em 0.25em 0.75em;
131: border-left: solid #9999FF 0.25em;
132: position: relative;
133: z-index: 1;
134: }
135: .element:before {
136: position: absolute;
137: z-index: 2;
138: top: 0;
139: left: -1.15em;
140: height: 2em;
141: width: 0.9em;
142: background: #EEEEFF;
143: content: ' ';
144: border-style: none none solid solid;
145: border-color: #9999FF;
146: border-width: 0.25em;
147: }
148:
149: .example { display: block; color: #222222; background: #FCFCFC; border-left: double; margin-left: 2em; padding-left: 1em; }
150: td > .example:only-child { margin: 0 0 0 0.1em; }
151:
152: ul.domTree, ul.domTree ul { padding: 0 0 0 1em; margin: 0; }
153: ul.domTree li { padding: 0; margin: 0; list-style: none; position: relative; }
154: ul.domTree li li { list-style: none; }
155: ul.domTree li:first-child::before { position: absolute; top: 0; height: 0.6em; left: -0.75em; width: 0.5em; border-style: none none solid solid; content: ''; border-width: 0.1em; }
156: ul.domTree li:not(:last-child)::after { position: absolute; top: 0; bottom: -0.6em; left: -0.75em; width: 0.5em; border-style: none none solid solid; content: ''; border-width: 0.1em; }
157: ul.domTree span { font-style: italic; font-family: serif; }
158: ul.domTree .t1 code { color: purple; font-weight: bold; }
159: ul.domTree .t2 { font-style: normal; font-family: monospace; }
160: ul.domTree .t2 .name { color: black; font-weight: bold; }
161: ul.domTree .t2 .value { color: blue; font-weight: normal; }
162: ul.domTree .t3 code, .domTree .t4 code, .domTree .t5 code { color: gray; }
163: ul.domTree .t7 code, .domTree .t8 code { color: green; }
164: ul.domTree .t10 code { color: teal; }
165:
166: body.dfnEnabled dfn { cursor: pointer; }
167: .dfnPanel {
168: display: inline;
169: position: absolute;
170: z-index: 10;
171: height: auto;
172: width: auto;
173: padding: 0.5em 0.75em;
174: font: small sans-serif, Droid Sans Fallback;
175: background: #DDDDDD;
176: color: black;
177: border: outset 0.2em;
178: }
179: .dfnPanel * { margin: 0; padding: 0; font: inherit; text-indent: 0; }
180: .dfnPanel :link, .dfnPanel :visited { color: black; }
181: .dfnPanel p { font-weight: bolder; }
182: .dfnPanel * + p { margin-top: 0.25em; }
183: .dfnPanel li { list-style-position: inside; }
184:
185: #configUI { position: absolute; z-index: 20; top: 10em; right: 1em; width: 11em; font-size: small; }
186: #configUI p { margin: 0.5em 0; padding: 0.3em; background: #EEEEEE; color: black; border: inset thin; }
187: #configUI p label { display: block; }
188: #configUI #updateUI, #configUI .loginUI { text-align: center; }
189: #configUI input[type=button] { display: block; margin: auto; }
190:
191: fieldset { margin: 1em; padding: 0.5em 1em; }
192: fieldset > legend + * { margin-top: 0; }
193: fieldset > :last-child { margin-bottom: 0; }
194: fieldset p { margin: 0.5em 0; }
195:
1.159 sruby 196: </style><link href="http://www.w3.org/StyleSheets/TR/W3C-ED" rel="stylesheet" type="text/css"><style type="text/css">
1.1 mike 197:
198: .applies thead th > * { display: block; }
199: .applies thead code { display: block; }
200: .applies tbody th { whitespace: nowrap; }
201: .applies td { text-align: center; }
202: .applies .yes { background: yellow; }
203:
204: .matrix, .matrix td { border: hidden; text-align: right; }
205: .matrix { margin-left: 2em; }
206:
207: .dice-example { border-collapse: collapse; border-style: hidden solid solid hidden; border-width: thin; margin-left: 3em; }
208: .dice-example caption { width: 30em; font-size: smaller; font-style: italic; padding: 0.75em 0; text-align: left; }
209: .dice-example td, .dice-example th { border: solid thin; width: 1.35em; height: 1.05em; text-align: center; padding: 0; }
210:
211: td.eg { border-width: thin; text-align: center; }
212:
213: #table-example-1 { border: solid thin; border-collapse: collapse; margin-left: 3em; }
214: #table-example-1 * { font-family: "Essays1743", serif; line-height: 1.01em; }
215: #table-example-1 caption { padding-bottom: 0.5em; }
216: #table-example-1 thead, #table-example-1 tbody { border: none; }
217: #table-example-1 th, #table-example-1 td { border: solid thin; }
218: #table-example-1 th { font-weight: normal; }
219: #table-example-1 td { border-style: none solid; vertical-align: top; }
220: #table-example-1 th { padding: 0.5em; vertical-align: middle; text-align: center; }
221: #table-example-1 tbody tr:first-child td { padding-top: 0.5em; }
222: #table-example-1 tbody tr:last-child td { padding-bottom: 1.5em; }
223: #table-example-1 tbody td:first-child { padding-left: 2.5em; padding-right: 0; width: 9em; }
224: #table-example-1 tbody td:first-child::after { content: leader(". "); }
225: #table-example-1 tbody td { padding-left: 2em; padding-right: 2em; }
226: #table-example-1 tbody td:first-child + td { width: 10em; }
227: #table-example-1 tbody td:first-child + td ~ td { width: 2.5em; }
228: #table-example-1 tbody td:first-child + td + td + td ~ td { width: 1.25em; }
229:
230: .apple-table-examples { border: none; border-collapse: separate; border-spacing: 1.5em 0em; width: 40em; margin-left: 3em; }
231: .apple-table-examples * { font-family: "Times", serif; }
232: .apple-table-examples td, .apple-table-examples th { border: none; white-space: nowrap; padding-top: 0; padding-bottom: 0; }
233: .apple-table-examples tbody th:first-child { border-left: none; width: 100%; }
234: .apple-table-examples thead th:first-child ~ th { font-size: smaller; font-weight: bolder; border-bottom: solid 2px; text-align: center; }
235: .apple-table-examples tbody th::after, .apple-table-examples tfoot th::after { content: leader(". ") }
236: .apple-table-examples tbody th, .apple-table-examples tfoot th { font: inherit; text-align: left; }
237: .apple-table-examples td { text-align: right; vertical-align: top; }
238: .apple-table-examples.e1 tbody tr:last-child td { border-bottom: solid 1px; }
239: .apple-table-examples.e1 tbody + tbody tr:last-child td { border-bottom: double 3px; }
240: .apple-table-examples.e2 th[scope=row] { padding-left: 1em; }
241: .apple-table-examples sup { line-height: 0; }
242:
243: .details-example img { vertical-align: top; }
244:
245: #base64-table {
246: white-space: nowrap;
247: font-size: 0.6em;
248: column-width: 6em;
249: column-count: 5;
250: column-gap: 1em;
251: -moz-column-width: 6em;
252: -moz-column-count: 5;
253: -moz-column-gap: 1em;
254: -webkit-column-width: 6em;
255: -webkit-column-count: 5;
256: -webkit-column-gap: 1em;
257: }
258: #base64-table thead { display: none; }
259: #base64-table * { border: none; }
260: #base64-table tbody td:first-child:after { content: ':'; }
261: #base64-table tbody td:last-child { text-align: right; }
262:
263: #named-character-references-table {
264: white-space: nowrap;
265: font-size: 0.6em;
266: column-width: 30em;
267: column-gap: 1em;
268: -moz-column-width: 30em;
269: -moz-column-gap: 1em;
270: -webkit-column-width: 30em;
271: -webkit-column-gap: 1em;
272: }
273: #named-character-references-table > table > tbody > tr > td:first-child + td,
274: #named-character-references-table > table > tbody > tr > td:last-child { text-align: center; }
275: #named-character-references-table > table > tbody > tr > td:last-child:hover > span { position: absolute; top: auto; left: auto; margin-left: 0.5em; line-height: 1.2; font-size: 5em; border: outset; padding: 0.25em 0.5em; background: white; width: 1.25em; height: auto; text-align: center; }
276: #named-character-references-table > table > tbody > tr#entity-CounterClockwiseContourIntegral > td:first-child { font-size: 0.5em; }
277:
278: .glyph.control { color: red; }
279:
280: @font-face {
281: font-family: 'Essays1743';
1.178 ! sruby 282: src: url('../fonts/Essays1743.ttf');
1.1 mike 283: }
284: @font-face {
285: font-family: 'Essays1743';
286: font-weight: bold;
1.178 ! sruby 287: src: url('../fonts/Essays1743-Bold.ttf');
1.1 mike 288: }
289: @font-face {
290: font-family: 'Essays1743';
291: font-style: italic;
1.178 ! sruby 292: src: url('../fonts/Essays1743-Italic.ttf');
1.1 mike 293: }
294: @font-face {
295: font-family: 'Essays1743';
296: font-style: italic;
297: font-weight: bold;
1.178 ! sruby 298: src: url('../fonts/Essays1743-BoldItalic.ttf');
1.1 mike 299: }
300:
1.159 sruby 301: </style><link href="data:text/css," id="complete" rel="stylesheet" title="Complete specification"><link href="data:text/css,.impl%20%7B%20display:%20none;%20%7D%0Ahtml%20%7B%20border:%20solid%20yellow;%20%7D%20.domintro:before%20%7B%20display:%20none;%20%7D" id="author" rel="alternate stylesheet" title="Author documentation only"><link href="data:text/css,.impl%20%7B%20background:%20%23FFEEEE;%20%7D%20.domintro:before%20%7B%20background:%20%23FFEEEE;%20%7D" id="highlight" rel="alternate stylesheet" title="Highlight implementation requirements"><script>
1.1 mike 302: function getCookie(name) {
303: var params = location.search.substr(1).split("&");
304: for (var index = 0; index < params.length; index++) {
305: if (params[index] == name)
306: return "1";
307: var data = params[index].split("=");
308: if (data[0] == name)
309: return unescape(data[1]);
310: }
311: var cookies = document.cookie.split("; ");
312: for (var index = 0; index < cookies.length; index++) {
313: var data = cookies[index].split("=");
314: if (data[0] == name)
315: return unescape(data[1]);
316: }
317: return null;
318: }
1.159 sruby 319: </script><link href="the-base-element.html" title="4.2.3 The base element" rel="prev">
1.161 sruby 320: <link href="spec.html#contents" title="Table of contents" rel="contents">
1.1 mike 321: <link href="the-meta-element.html" title="4.2.5 The meta element" rel="next">
1.22 mike 322: </head><body onload="fixBrokenLink();" class="split chapter"><div class="head" id="head">
1.1 mike 323: <p><a href="http://www.w3.org/"><img alt="W3C" height="48" src="http://www.w3.org/Icons/w3c_home" width="72"></a></p>
324:
325: <h1>HTML5</h1>
1.159 sruby 326: <h2 class="no-num no-toc" id="a-vocabulary-and-associated-apis-for-html-and-xhtml">A vocabulary and associated APIs for HTML and XHTML</h2>
1.178 ! sruby 327: <h2 class="no-num no-toc" id="editor's-draft-date-1-january-1970">Editor's Draft 17 September 2012</h2>
1.85 mike 328: </div>
1.174 sruby 329: <div class="prev_next">
1.1 mike 330: <a href="the-base-element.html">← 4.2.3 The base element</a> –
1.161 sruby 331: <a href="spec.html#contents">Table of contents</a> –
1.1 mike 332: <a href="the-meta-element.html">4.2.5 The meta element →</a>
1.159 sruby 333: </div>
1.1 mike 334:
1.85 mike 335: <h4 id="the-link-element"><span class="secno">4.2.4 </span>The <dfn><code>link</code></dfn> element</h4>
336:
337: <dl class="element"><dt><a href="element-definitions.html#element-dfn-categories" title="element-dfn-categories">Categories</a>:</dt>
1.159 sruby 338: <dd><a href="content-models.html#metadata-content-0">Metadata content</a>.</dd>
339: <!--MD-->
1.25 mike 340: <dt><a href="element-definitions.html#element-dfn-contexts" title="element-dfn-contexts">Contexts in which this element can be used</a>:</dt>
1.159 sruby 341: <dd>Where <a href="content-models.html#metadata-content-0">metadata content</a> is expected.</dd>
1.1 mike 342: <dd>In a <code><a href="the-noscript-element.html#the-noscript-element">noscript</a></code> element that is a child of a <code><a href="the-head-element.html#the-head-element">head</a></code> element.</dd>
1.159 sruby 343: <!--MD-->
1.25 mike 344: <dt><a href="element-definitions.html#element-dfn-content-model" title="element-dfn-content-model">Content model</a>:</dt>
1.1 mike 345: <dd>Empty.</dd>
1.25 mike 346: <dt><a href="element-definitions.html#element-dfn-attributes" title="element-dfn-attributes">Content attributes</a>:</dt>
1.1 mike 347: <dd><a href="global-attributes.html#global-attributes">Global attributes</a></dd>
348: <dd><code title="attr-link-href"><a href="#attr-link-href">href</a></code></dd>
349: <dd><code title="attr-link-rel"><a href="#attr-link-rel">rel</a></code></dd>
350: <dd><code title="attr-link-media"><a href="#attr-link-media">media</a></code></dd>
351: <dd><code title="attr-link-hreflang"><a href="#attr-link-hreflang">hreflang</a></code></dd>
352: <dd><code title="attr-link-type"><a href="#attr-link-type">type</a></code></dd>
353: <dd><code title="attr-link-sizes"><a href="links.html#attr-link-sizes">sizes</a></code></dd>
354: <dd>Also, the <code title="attr-link-title"><a href="#attr-link-title">title</a></code> attribute has special semantics on this element.</dd>
1.159 sruby 355: <dt><a href="element-definitions.html#element-dfn-dom" title="element-dfn-dom">DOM interface</a>:</dt><!--TOPIC:DOM APIs-->
1.1 mike 356: <dd>
357: <pre class="idl">interface <dfn id="htmllinkelement">HTMLLinkElement</dfn> : <a href="elements.html#htmlelement">HTMLElement</a> {
358: attribute boolean <a href="#dom-link-disabled" title="dom-link-disabled">disabled</a>;
359: attribute DOMString <a href="#dom-link-href" title="dom-link-href">href</a>;
360: attribute DOMString <a href="#dom-link-rel" title="dom-link-rel">rel</a>;
361: readonly attribute <a href="infrastructure.html#domtokenlist">DOMTokenList</a> <a href="#dom-link-rellist" title="dom-link-relList">relList</a>;
362: attribute DOMString <a href="#dom-link-media" title="dom-link-media">media</a>;
363: attribute DOMString <a href="#dom-link-hreflang" title="dom-link-hreflang">hreflang</a>;
364: attribute DOMString <a href="#dom-link-type" title="dom-link-type">type</a>;
365: [PutForwards=<span title="dom-DOMSettableTokenList-value">value</span>] readonly attribute <a href="infrastructure.html#domsettabletokenlist">DOMSettableTokenList</a> <a href="#dom-link-sizes" title="dom-link-sizes">sizes</a>;
366: };
367: <a href="#htmllinkelement">HTMLLinkElement</a> implements <a href="infrastructure.html#linkstyle">LinkStyle</a>;</pre>
368: </dd>
1.159 sruby 369: </dl><!--TOPIC:HTML--><p>The <code><a href="#the-link-element">link</a></code> element allows authors to link their
1.85 mike 370: document to other resources.</p>
371:
372: <p>The destination of the link(s) is given by the <dfn id="attr-link-href" title="attr-link-href"><code>href</code></dfn> attribute, which must
1.1 mike 373: be present and must contain a <a href="urls.html#valid-non-empty-url-potentially-surrounded-by-spaces">valid non-empty URL potentially
374: surrounded by spaces</a>. <span class="impl">If the <code title="attr-link-href"><a href="#attr-link-href">href</a></code> attribute is absent, then the
1.85 mike 375: element does not define a link.</span></p>
376:
1.159 sruby 377: <!--MD--><!--MD-->
1.85 mike 378: <p>A <code><a href="#the-link-element">link</a></code> element must have <code title="attr-link-rel"><a href="#attr-link-rel">rel</a></code> attribute.</p>
1.159 sruby 379: <!--MD-->
1.85 mike 380:
381: <p>The types of link indicated (the relationships) are given by the
1.1 mike 382: value of the <dfn id="attr-link-rel" title="attr-link-rel"><code>rel</code></dfn>
383: attribute, which, if present, must have a value that is a <a href="common-microsyntaxes.html#set-of-space-separated-tokens">set
384: of space-separated tokens</a>. The <a href="links.html#linkTypes">allowed
385: keywords and their meanings</a> are defined in a later
386: section. <span class="impl">If the <code title="attr-link-rel"><a href="#attr-link-rel">rel</a></code> attribute is absent, has no
387: keywords, or if none of the keywords used are allowed according to
388: the definitions in this specification, then the element does not
1.85 mike 389: create any links.</span></p>
390:
391: <p>Two categories of links can be created using the
1.1 mike 392: <code><a href="#the-link-element">link</a></code> element: <a href="links.html#external-resource-link" title="external resource
393: link">Links to external resources</a> and <a href="links.html#hyperlink" title="hyperlink">hyperlinks</a>. The <a href="links.html#linkTypes">link
394: types section</a> defines whether a particular link type is an
395: external resource or a hyperlink. One <code><a href="#the-link-element">link</a></code> element can
396: create multiple links (of which some might be external resource
397: links and some might be hyperlinks); exactly which and how many
398: links are created depends on the keywords given in the <code title="attr-link-rel"><a href="#attr-link-rel">rel</a></code> attribute. User agents must process
1.85 mike 399: the links on a per-link basis, not a per-element basis.</p>
400:
401: <p class="note">Each link created for a <code><a href="#the-link-element">link</a></code> element is
1.1 mike 402: handled separately. For instance, if there are two <code><a href="#the-link-element">link</a></code>
403: elements with <code title="">rel="stylesheet"</code>, they each
404: count as a separate external resource, and each is affected by its
405: own attributes independently. Similarly, if a single
406: <code><a href="#the-link-element">link</a></code> element has a <code title="attr-link-rel"><a href="#attr-link-rel">rel</a></code> attribute with the value <code title="">next stylesheet</code>, it creates both a
407: <a href="links.html#hyperlink">hyperlink</a> (for the <code title="rel-next"><a href="links.html#link-type-next">next</a></code>
408: keyword) and an <a href="links.html#external-resource-link">external resource link</a> (for the <code title="rel-stylesheet"><a href="links.html#link-type-stylesheet">stylesheet</a></code> keyword), and they are
1.85 mike 409: affected by other attributes (such as <code title="attr-link-media"><a href="#attr-link-media">media</a></code> or <code title="attr-link-title"><a href="#attr-link-title">title</a></code>) differently.</p>
410:
411: <div class="example">
1.1 mike 412:
413: <p>For example, the following <code><a href="#the-link-element">link</a></code> element creates two
414: hyperlinks (to the same page):</p>
415:
416: <pre><link rel="author license" href="/about"></pre>
417:
418: <p>The two links created by this element are one whose semantic is
419: that the target page has information about the current page's
420: author, and one whose semantic is that the target page has
421: information regarding the license under which the current page is
422: provided.</p>
423:
1.85 mike 424: </div>
425:
426: <p>The exact behavior for links to external resources depends on the
1.1 mike 427: exact relationship, as defined for the relevant link type. Some of
428: the attributes control whether or not the external resource is to be
1.85 mike 429: applied (as defined below).</p>
430:
431: <div class="impl">
1.1 mike 432:
433: <p>For external resources that are represented in the
434: DOM (for example, style sheets), the DOM representation must be made
435: available even if the resource is not applied. To <dfn id="concept-link-obtain" title="concept-link-obtain">obtain the resource</dfn>, the user
436: agent must run the following steps:</p>
437:
438: <ol><li><p>If the <code title="attr-link-href"><a href="#attr-link-href">href</a></code> attribute's
439: value is the empty string, then abort these steps.</p></li>
440:
441: <li><p><a href="urls.html#resolve-a-url" title="resolve a url">Resolve</a> the
442: <a href="urls.html#url">URL</a> given by the <code title="attr-link-href"><a href="#attr-link-href">href</a></code> attribute, relative to the
443: element.</p></li>
444:
445: <li><p>If the previous step fails, then abort these steps.</p></li>
446:
447: <li><p><a href="urls.html#fetch">Fetch</a> the resulting <a href="urls.html#absolute-url">absolute
1.159 sruby 448: URL</a>.</p></li> <!-- http-origin privacy sensitive -->
1.1 mike 449:
450: </ol><p>User agents may opt to only try to obtain such resources when
451: they are needed, instead of pro-actively <a href="urls.html#fetch" title="fetch">fetching</a> all the external resources that are
452: not applied.</p>
453:
454: <p>The semantics of the protocol used (e.g. HTTP) must be followed
455: when fetching external resources. (For example, redirects will be
456: followed and 404 responses will cause the external resource to not
457: be applied.)</p>
458:
1.159 sruby 459: <!-- the next few paragraph are similar to text in the <style> section -->
1.1 mike 460: <p>Once the attempts to obtain the resource and its <a href="infrastructure.html#critical-subresources">critical
461: subresources</a> are complete, the user agent must, if the loads
462: were successful, <a href="webappapis.html#queue-a-task">queue a task</a> to <a href="webappapis.html#fire-a-simple-event">fire a simple
463: event</a> named <code title="event-load">load</code> at the
464: <code><a href="#the-link-element">link</a></code> element, or, if the resource or one of its
465: <a href="infrastructure.html#critical-subresources">critical subresources</a> failed to completely load for any
466: reason (e.g. DNS error, HTTP 404 response, a connection being
467: prematurely closed, unsupported Content-Type), <a href="webappapis.html#queue-a-task">queue a
468: task</a> to <a href="webappapis.html#fire-a-simple-event">fire a simple event</a> named <code title="event-error">error</code> at the <code><a href="#the-link-element">link</a></code>
469: element. Non-network errors in processing the resource or its
470: subresources (e.g. CSS parse errors, PNG decoding errors) are not
471: failures for the purposes of this paragraph.</p>
472:
473: <p>The <a href="webappapis.html#task-source">task source</a> for these <a href="webappapis.html#concept-task" title="concept-task">tasks</a> is the <a href="webappapis.html#dom-manipulation-task-source">DOM manipulation task
474: source</a>.</p>
475:
476: <p>The element must <a href="the-end.html#delay-the-load-event">delay the load event</a> of the
477: element's document until all the attempts to obtain the resource and
478: its <a href="infrastructure.html#critical-subresources">critical subresources</a> are complete. (Resources that
479: the user agent has not yet attempted to obtain, e.g. because it is
480: waiting for the resource to be needed, do not <a href="the-end.html#delay-the-load-event">delay the load
481: event</a>.)</p>
482:
483: <hr><p id="linkui">Interactive user agents may provide users with a
1.159 sruby 484: means to <a href="links.html#following-hyperlinks-0" title="following hyperlinks">follow the
1.1 mike 485: hyperlinks</a> created using the <code><a href="#the-link-element">link</a></code> element,
486: somewhere within their user interface. The exact interface is not
487: defined by this specification, but it could include the following
488: information (obtained from the element's attributes, again as
489: defined below), in some form or another (possibly simplified), for
490: each hyperlink created with each <code><a href="#the-link-element">link</a></code> element in the
491: document:</p>
492:
1.159 sruby 493: <ul><!-- the order here is the order that makes most sense for a UI --><li>The relationship between this document and the resource (given
1.1 mike 494: by the <code title="attr-link-rel"><a href="#attr-link-rel">rel</a></code> attribute)</li>
495:
496: <li>The title of the resource (given by the <code title="attr-link-title"><a href="#attr-link-title">title</a></code> attribute).</li>
497:
498: <li>The address of the resource (given by the <code title="attr-link-href"><a href="#attr-link-href">href</a></code> attribute).</li>
499:
500: <li>The language of the resource (given by the <code title="attr-link-hreflang"><a href="#attr-link-hreflang">hreflang</a></code> attribute).</li>
501:
502: <li>The optimum media for the resource (given by the <code title="attr-link-media"><a href="#attr-link-media">media</a></code> attribute).</li>
503:
504: </ul><p>User agents could also include other information, such as the
505: type of the resource (as given by the <code title="attr-link-type"><a href="#attr-link-type">type</a></code> attribute).</p>
506:
1.85 mike 507: </div>
508:
509: <p class="note">Hyperlinks created with the <code><a href="#the-link-element">link</a></code>
1.1 mike 510: element and its <code title="attr-link-rel"><a href="#attr-link-rel">rel</a></code> attribute
511: apply to the whole page. This contrasts with the <code title="attr-hyperlink-rel"><a href="links.html#attr-hyperlink-rel">rel</a></code> attribute of <code><a href="the-a-element.html#the-a-element">a</a></code>
512: and <code><a href="the-area-element.html#the-area-element">area</a></code> elements, which indicates the type of a link
513: whose context is given by the link's location within the
1.85 mike 514: document.</p>
515:
516: <p>The <dfn id="attr-link-media" title="attr-link-media"><code>media</code></dfn>
1.1 mike 517: attribute says which media the resource applies to. The value must
1.85 mike 518: be a <a href="common-microsyntaxes.html#valid-media-query">valid media query</a>.</p>
519:
520: <div class="impl">
1.1 mike 521:
522: <p>If the link is a <a href="links.html#hyperlink">hyperlink</a> then the <code title="attr-link-media"><a href="#attr-link-media">media</a></code> attribute is purely advisory,
523: and describes for which media the document in question was
524: designed.</p>
525:
526: <p>However, if the link is an <a href="links.html#external-resource-link">external resource link</a>,
527: then the <code title="attr-link-media"><a href="#attr-link-media">media</a></code> attribute is
528: prescriptive. The user agent must apply the external resource when
529: the <code title="attr-link-media"><a href="#attr-link-media">media</a></code> attribute's value
530: <a href="common-microsyntaxes.html#matches-the-environment">matches the environment</a> and the other relevant
1.159 sruby 531: conditions apply, and must not apply it otherwise.</p><!-- note
532: similar text in <style> section -->
1.4 mike 533:
1.1 mike 534: <p class="note">The external resource might have further
535: restrictions defined within that limit its applicability. For
536: example, a CSS style sheet might have some <code title="">@media</code> blocks. This specification does not override
1.159 sruby 537: such further restrictions or requirements.</p><!-- note similar text
538: in <style> section -->
1.4 mike 539:
1.85 mike 540: </div>
541:
542: <p id="default-media">The default, if the <code title="attr-link-media"><a href="#attr-link-media">media</a></code> attribute is omitted, is "<code title="">all</code>", meaning that by default links apply to all
543: media.</p>
544:
545: <p>The <dfn id="attr-link-hreflang" title="attr-link-hreflang"><code>hreflang</code></dfn>
1.1 mike 546: attribute on the <code><a href="#the-link-element">link</a></code> element has the same semantics as
547: the <a href="links.html#attr-hyperlink-hreflang" title="attr-hyperlink-hreflang"><code>hreflang</code>
548: attribute on <code>a</code> and <code>area</code>
1.85 mike 549: elements</a>.</p>
550:
551: <p>The <dfn id="attr-link-type" title="attr-link-type"><code>type</code></dfn> attribute
1.1 mike 552: gives the <a href="infrastructure.html#mime-type">MIME type</a> of the linked resource. It is
553: purely advisory. The value must be a <a href="infrastructure.html#valid-mime-type">valid MIME
1.85 mike 554: type</a>.</p>
555:
556: <p>For <a href="links.html#external-resource-link" title="external resource link">external resource
1.1 mike 557: links</a>, the <code title="attr-link-type"><a href="#attr-link-type">type</a></code> attribute
558: is used as a hint to user agents so that they can avoid fetching
559: resources they do not support. <span class="impl">If the attribute
560: is present, then the user agent must assume that the resource is of
561: the given type (even if that is not a <a href="infrastructure.html#valid-mime-type">valid MIME type</a>,
562: e.g. the empty string). If the attribute is omitted, but the
563: external resource link type has a default type defined, then the
564: user agent must assume that the resource is of that type. If the UA
565: does not support the given <a href="infrastructure.html#mime-type">MIME type</a> for the given link
566: relationship, then the UA should not <a href="#concept-link-obtain" title="concept-link-obtain">obtain</a> the resource; if the UA
567: does support the given <a href="infrastructure.html#mime-type">MIME type</a> for the given link
568: relationship, then the UA should <a href="#concept-link-obtain" title="concept-link-obtain">obtain</a> the resource at the
569: appropriate time as specified for the <a href="links.html#external-resource-link">external resource
570: link</a>'s particular type. If the attribute is omitted, and the
571: external resource link type does not have a default type defined,
572: but the user agent would <a href="#concept-link-obtain" title="concept-link-obtain">obtain</a> the resource if the type
573: was known and supported, then the user agent should <a href="#concept-link-obtain" title="concept-link-obtain">obtain</a> the resource under the
1.85 mike 574: assumption that it will be supported.</span></p>
575:
576: <div class="impl">
1.1 mike 577:
578: <p>User agents must not consider the <code title="attr-link-type"><a href="#attr-link-type">type</a></code> attribute authoritative —
579: upon fetching the resource, user agents must not use the <code title="attr-link-type"><a href="#attr-link-type">type</a></code> attribute to determine its actual
580: type. Only the actual type (as defined in the next paragraph) is
581: used to determine whether to <em>apply</em> the resource, not the
582: aforementioned assumed type.</p>
583:
584: <p id="concept-link-type-sniffing">If the external resource link
585: type defines rules for processing the resource's <a href="urls.html#content-type" title="Content-Type">Content-Type metadata</a>, then those rules
586: apply. Otherwise, if the resource is expected to be an image, user
587: agents may apply the <a href="urls.html#content-type-sniffing:-image" title="Content-Type sniffing:
588: image">image sniffing rules</a>, with the <var title="">official
589: type</var> being the type determined from the resource's <a href="urls.html#content-type" title="Content-Type">Content-Type metadata</a>, and use the
590: resulting sniffed type of the resource as if it was the actual
591: type. Otherwise, if neither of these conditions apply or if the user
592: agent opts not to apply the image sniffing rules, then the user
593: agent must use the resource's <a href="urls.html#content-type" title="Content-Type">Content-Type metadata</a> to determine the
594: type of the resource. If there is no type metadata, but the external
595: resource link type has a default type defined, then the user agent
596: must assume that the resource is of that type.</p>
597:
598: <p class="note">The <code title="rel-stylesheet"><a href="links.html#link-type-stylesheet">stylesheet</a></code>
599: link type defines rules for processing the resource's <a href="urls.html#content-type" title="Content-Type">Content-Type metadata</a>.</p>
600:
601: <p>Once the user agent has established the type of the resource, the
602: user agent must apply the resource if it is of a supported type and
603: the other relevant conditions apply, and must ignore the resource
604: otherwise.</p>
605:
606: <div class="example">
607:
608: <p>If a document contains style sheet links labeled as follows:</p>
609:
610: <pre><link rel="stylesheet" href="A" type="text/plain">
611: <link rel="stylesheet" href="B" type="text/css">
612: <link rel="stylesheet" href="C"></pre>
613:
614: <p>...then a compliant UA that supported only CSS style sheets
615: would fetch the B and C files, and skip the A file (since
616: <code>text/plain</code> is not the <a href="infrastructure.html#mime-type">MIME type</a> for CSS style
617: sheets).</p>
618:
619: <p>For files B and C, it would then check the actual types returned
620: by the server. For those that are sent as <code>text/css</code>, it
621: would apply the styles, but for those labeled as
622: <code>text/plain</code>, or any other type, it would not.</p>
623:
624: <p>If one of the two files was returned without a
625: <a href="urls.html#content-type">Content-Type</a> metadata, or with a syntactically
626: incorrect type like <code title="">Content-Type: "null"</code>, then the default type
627: for <code title="rel-stylesheet"><a href="links.html#link-type-stylesheet">stylesheet</a></code> links would kick
628: in. Since that default type is <code title="">text/css</code>, the
629: style sheet <em>would</em> nonetheless be applied.</p>
630:
631: </div>
632:
1.85 mike 633: </div>
634:
635: <p>The <dfn id="attr-link-title" title="attr-link-title"><code>title</code></dfn>
1.1 mike 636: attribute gives the title of the link. With one exception, it is
637: purely advisory. The value is text. The exception is for style sheet
638: links, where the <code title="attr-link-title"><a href="#attr-link-title">title</a></code>
1.85 mike 639: attribute defines <a href="infrastructure.html#alternative-style-sheet-sets">alternative style sheet sets</a>.</p>
640:
641: <p class="note">The <code title="attr-link-title"><a href="#attr-link-title">title</a></code>
1.1 mike 642: attribute on <code><a href="#the-link-element">link</a></code> elements differs from the global
643: <code title="attr-title"><a href="global-attributes.html#the-title-attribute">title</a></code> attribute of most other
644: elements in that a link without a title does not inherit the title
1.85 mike 645: of the parent element: it merely has no title.</p>
646:
647: <p>The <code title="attr-link-sizes"><a href="links.html#attr-link-sizes">sizes</a></code> attribute is used
1.1 mike 648: with the <code title="rel-icon"><a href="links.html#rel-icon">icon</a></code> link type. The attribute
649: must not be specified on <code><a href="#the-link-element">link</a></code> elements that do not have
650: a <code title="attr-link-rel"><a href="#attr-link-rel">rel</a></code> attribute that specifies
1.85 mike 651: the <code title="rel-icon"><a href="links.html#rel-icon">icon</a></code> keyword.</p>
652:
653: <div class="impl">
1.1 mike 654:
1.159 sruby 655: <!--!--><!-- s/header fields/headers/ for consistency with the rest of the spec -->
1.50 mike 656:
657: <p>HTTP <code title="http-link">Link:</code> header fields, if
658: supported, must be assumed to come before any links in the document,
659: in the order that they were given in the HTTP message. These header
660: fields are to be processed according to the rules given in the
1.159 sruby 661: relevant specifications. <a href="references.html#refsHTTP">[HTTP]</a> <a href="references.html#refsWEBLINK">[WEBLINK]</a></p> <!-- WEBLINK is ref for Link:
662: header -->
1.50 mike 663:
664: <p class="note">Registration of relation types in HTTP Link: header
665: fields is distinct from <a href="links.html#linkTypes">HTML link types</a>,
666: and thus their semantics can be different from same-named HTML
667: types.</p>
1.4 mike 668:
1.1 mike 669: <p>The IDL attributes <dfn id="dom-link-href" title="dom-link-href"><code>href</code></dfn>, <dfn id="dom-link-rel" title="dom-link-rel"><code>rel</code></dfn>, <dfn id="dom-link-media" title="dom-link-media"><code>media</code></dfn>, <dfn id="dom-link-hreflang" title="dom-link-hreflang"><code>hreflang</code></dfn>, <dfn id="dom-link-type" title="dom-link-type"><code>type</code></dfn>, and <dfn id="dom-link-sizes" title="dom-link-sizes"><code>sizes</code></dfn> each must
670: <a href="common-dom-interfaces.html#reflect">reflect</a> the respective content attributes of the same
671: name.</p>
672:
673: <p>The IDL attribute <dfn id="dom-link-rellist" title="dom-link-rellist"><code>relList</code></dfn> <span class="impl">must</span> <a href="common-dom-interfaces.html#reflect" title="reflect">reflect</a> the <code title="attr-link-rel"><a href="#attr-link-rel">rel</a></code> content attribute.</p>
674:
1.85 mike 675: </div>
676:
677: <p>The IDL attribute <dfn id="dom-link-disabled" title="dom-link-disabled"><code>disabled</code></dfn> only applies
1.1 mike 678: to style sheet links. When the <code><a href="#the-link-element">link</a></code> element defines a
679: style sheet link, then the <code title="dom-link-disabled"><a href="#dom-link-disabled">disabled</a></code> attribute behaves as
680: defined <a href="styling.html#dom-linkstyle-disabled" title="dom-linkstyle-disabled">for the alternative
681: style sheets DOM</a>. For all other <code><a href="#the-link-element">link</a></code> elements it
1.159 sruby 682: always return false and does nothing on setting.</p> <!-- that is
683: normatively required in the definition of dom-linkstyle-disabled -->
1.85 mike 684:
685: <p>The <code><a href="infrastructure.html#linkstyle">LinkStyle</a></code> interface is also implemented by
1.1 mike 686: this element; the <a href="styling.html#styling">styling processing model</a> defines
1.85 mike 687: how. <a href="references.html#refsCSSOM">[CSSOM]</a></p>
688:
689: <div class="example">
1.1 mike 690:
691: <p>Here, a set of <code><a href="#the-link-element">link</a></code> elements provide some style
692: sheets:</p>
693:
694: <pre><!-- a persistent style sheet -->
695: <link rel="stylesheet" href="default.css">
696:
697: <!-- the preferred alternate style sheet -->
698: <link rel="stylesheet" href="green.css" title="Green styles">
699:
700: <!-- some alternate style sheets -->
701: <link rel="alternate stylesheet" href="contrast.css" title="High contrast">
702: <link rel="alternate stylesheet" href="big.css" title="Big fonts">
703: <link rel="alternate stylesheet" href="wide.css" title="Wide screen"></pre>
704:
1.85 mike 705: </div>
706:
707: <div class="example">
1.1 mike 708:
709: <p>The following example shows how you can specify versions of the
710: page that use alternative formats, are aimed at other languages,
711: and that are intended for other media:</p>
712:
713: <pre><link rel=alternate href="/en/html" hreflang=en type=text/html title="English HTML">
714: <link rel=alternate href="/fr/html" hreflang=fr type=text/html title="French HTML">
715: <link rel=alternate href="/en/html/print" hreflang=en type=text/html media=print title="English HTML (for printing)">
716: <link rel=alternate href="/fr/html/print" hreflang=fr type=text/html media=print title="French HTML (for printing)">
717: <link rel=alternate href="/en/pdf" hreflang=en type=application/pdf title="English PDF">
718: <link rel=alternate href="/fr/pdf" hreflang=fr type=application/pdf title="French PDF"></pre>
719:
1.85 mike 720: </div>
721:
722:
723:
724:
725:
726: </body></html>
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