'vertical-align' keywords aren't animatable because nobody knows how the animation is supposed to work.

This resolves https://www.w3.org/Bugs/Public/show_bug.cgi?id=14988
as proposed in
http://lists.w3.org/Archives/Public/www-style/2012Mar/0013.html and
resolved in the 2012 February 29 teleconference (minutes at
http://lists.w3.org/Archives/Public/www-style/2012Mar/0013.html ).

Author: dbaron

css3-transitions/Overview.html

@@ -1404,7 +1404,7 @@ <h3 id=properties-from-css-><span class=secno>7.1. </span> Properties from
     <tr>
      <td>vertical-align
 
-     <td>keywords, length, percentage
+     <td>length, percentage
 
     <tr>
      <td>visibility

css3-transitions/Overview.src.html

@@ -1314,7 +1314,7 @@ <h3>
          <td>top</td><td>length, percentage</td>
        </tr>
        <tr>
-         <td>vertical-align</td><td>keywords, length, percentage</td>
+         <td>vertical-align</td><td>length, percentage</td>
        </tr>
        <tr>
          <td>visibility</td><td>visibility</td>