[e] (0) Be more explicit about requirements.

Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=22499
Affected topics: HTML

git-svn-id: http://svn.whatwg.org/webapps@8018 340c8d12-0b0e-0410-8428-c7bf67bfef74

complete.html

@@ -12303,7 +12303,7 @@ <h4 id=the-head-element><span class=secno>4.2.1 </span>The <dfn><code>head</code
    <dt><a href=#element-dfn-contexts title=element-dfn-contexts>Contexts in which this element can be used</a>:</dt>
    <dd>As the first element in an <code><a href=#the-html-element>html</a></code> element.</dd>
    <dt><a href=#element-dfn-content-model title=element-dfn-content-model>Content model</a>:</dt>
-   <dd>If the document is <a href=#an-iframe-srcdoc-document>an <code>iframe</code> <code title=attr-iframe-srcdoc>srcdoc</code> document</a> or if title information is available from a higher-level protocol: Zero or more elements of <a href=#metadata-content>metadata content</a>.</dd>
+   <dd>If the document is <a href=#an-iframe-srcdoc-document>an <code>iframe</code> <code title=attr-iframe-srcdoc>srcdoc</code> document</a> or if title information is available from a higher-level protocol: Zero or more elements of <a href=#metadata-content>metadata content</a>, of which no more than one is a <code><a href=#the-title-element>title</a></code> element.</dd>
    <dd>Otherwise: One or more elements of <a href=#metadata-content>metadata content</a>, of which exactly one is a <code><a href=#the-title-element>title</a></code> element.</dd>
    <dt><a href=#element-dfn-tag-omission title=element-dfn-tag-omission>Tag omission in text/html</a>:</dt>
    <dd>A <code><a href=#the-head-element>head</a></code> element's <a href=#syntax-start-tag title=syntax-start-tag>start tag</a> can be omitted if the

index

@@ -12303,7 +12303,7 @@ gave me some of the songs they wrote. I love sharing my music.</p>
    <dt><a href=#element-dfn-contexts title=element-dfn-contexts>Contexts in which this element can be used</a>:</dt>
    <dd>As the first element in an <code><a href=#the-html-element>html</a></code> element.</dd>
    <dt><a href=#element-dfn-content-model title=element-dfn-content-model>Content model</a>:</dt>
-   <dd>If the document is <a href=#an-iframe-srcdoc-document>an <code>iframe</code> <code title=attr-iframe-srcdoc>srcdoc</code> document</a> or if title information is available from a higher-level protocol: Zero or more elements of <a href=#metadata-content>metadata content</a>.</dd>
+   <dd>If the document is <a href=#an-iframe-srcdoc-document>an <code>iframe</code> <code title=attr-iframe-srcdoc>srcdoc</code> document</a> or if title information is available from a higher-level protocol: Zero or more elements of <a href=#metadata-content>metadata content</a>, of which no more than one is a <code><a href=#the-title-element>title</a></code> element.</dd>
    <dd>Otherwise: One or more elements of <a href=#metadata-content>metadata content</a>, of which exactly one is a <code><a href=#the-title-element>title</a></code> element.</dd>
    <dt><a href=#element-dfn-tag-omission title=element-dfn-tag-omission>Tag omission in text/html</a>:</dt>
    <dd>A <code><a href=#the-head-element>head</a></code> element's <a href=#syntax-start-tag title=syntax-start-tag>start tag</a> can be omitted if the

source

@@ -12536,7 +12536,7 @@ gave me some of the songs they wrote. I love sharing my music.</p>
    <dt><span title="element-dfn-contexts">Contexts in which this element can be used</span>:</dt>
    <dd>As the first element in an <code>html</code> element.</dd>
    <dt><span title="element-dfn-content-model">Content model</span>:</dt>
-   <dd>If the document is <span>an <code>iframe</code> <code title="attr-iframe-srcdoc">srcdoc</code> document</span> or if title information is available from a higher-level protocol: Zero or more elements of <span>metadata content</span>.</dd>
+   <dd>If the document is <span>an <code>iframe</code> <code title="attr-iframe-srcdoc">srcdoc</code> document</span> or if title information is available from a higher-level protocol: Zero or more elements of <span>metadata content</span>, of which no more than one is a <code>title</code> element.</dd>
    <dd>Otherwise: One or more elements of <span>metadata content</span>, of which exactly one is a <code>title</code> element.</dd>
    <dt><span title="element-dfn-attributes">Content attributes</span>:</dt>
    <dd><span>Global attributes</span></dd>