[css-content] add comment to alt example per James Craig feedback

Author: dauwhe

css-content/Overview.bs

@@ -349,7 +349,7 @@ Alternative text for Generated Content: The 'alt' property</h3>
   <pre>
   .new::before { 
     content: url(./img/star.png);
-    alt: "New!"; 
+    alt: "New!"; /* or a lcoalized attribute from the DOM: attr("data-alt") */
   }
   </pre>
   </div>

css-content/Overview.html

@@ -54,7 +54,7 @@
 </p>
   <h1 class="p-name no-ref" id=title>CSS Generated Content Module Level 3</h1>
   <h2 class="no-num no-toc no-ref heading settled" id=subtitle><span class=content>Editor’s Draft,
-    <span class=dt-updated><span class=value-title title=20141205>5 December 2014</span></span></span></h2>
+    <time class=dt-updated datetime=2015-01-12>12 January 2015</time></span></h2>
   <div data-fill-with=spec-metadata><dl><dt>This version:<dd><a class=u-url href=http://dev.w3.org/csswg/css-content/>http://dev.w3.org/csswg/css-content/</a><dt>Latest version:<dd><a href=http://www.w3.org/TR/css3-content/>http://www.w3.org/TR/css3-content/</a><dt>Previous Versions:<dd><a href=http://www.w3.org/TR/2003/WD-css3-content-20030514/ rel=previous>http://www.w3.org/TR/2003/WD-css3-content-20030514/</a><dt>Feedback:<dd><span><a href="mailto:www-style@w3.org?subject=%5Bcss-content%5D%20feedback">www-style@w3.org</a> with subject line “<kbd>[css-content] <var>… message topic …</var></kbd>” (<a href=http://lists.w3.org/Archives/Public/www-style/ rel=discussion>archives</a>)</span><dt>Issue Tracking:<dd><a href=#issues-index>Inline In Spec</a><dt class=editor>Editors:<dd class=editor><div class="p-author h-card vcard"><a class="p-name fn u-url url" href=http://fantasai.inkedblade.net/contact>Fantasai</a> (<span class="p-org org">W3C Invited Expert</span>)</div><dd class=editor><div class="p-author h-card vcard"><a class="p-name fn u-email email" href=mailto:dauwhe@gmail.com>Dave Cramer</a> (<span class="p-org org">Hachette Livre</span>)</div><dt>Former Editors:<dd><div class="p-author h-card vcard"><a class="p-name fn u-email email" href=mailto:howcome@opera.com>Håkon Wium Lie</a> (<span class="p-org org">Opera Software</span>)</div><dd><div class="p-author h-card vcard"><a class="p-name fn u-email email" href=mailto:ian@hixie.ch>Ian Hickson</a> (<span class="p-org org">Google</span>)</div></dl></div>
   <div data-fill-with=warning><details class=annoying-warning open>
 	<summary>Not Ready For Implementation</summary>
@@ -417,7 +417,7 @@ <h3 class="heading settled" data-level=2.1 id=alt-property><span class=secno>2.1
 
   <pre>.new::before { 
   content: url(./img/star.png);
-  alt: "New!"; 
+  alt: "New!"; /* or a lcoalized attribute from the DOM: attr("data-alt") */
 }
 </pre>
   </div>