--- a/webvtt/webvtt.html	Sat Nov 09 11:49:25 2013 +1100
+++ b/webvtt/webvtt.html	Sat Nov 09 12:47:36 2013 +1100
@@ -770,7 +770,7 @@
 	    <a title="text track cue writing direction">writing direction</a>, otherwise to be interpreted
 	    as a percentage of the region width.</p>
 	
-     <p>A <a>text track cue</a> has a default <a>text track cue text position</a> which is defined
+     <p>A <a>text track cue</a> has a <df>default text track cue text position</dfn> which is defined
      in terms of the value of the <a>text track cue text alignment</a>:</p>
      
      <ol>
@@ -829,8 +829,8 @@
 
       </dl>
 
-      <p>A <a>text track cue</a> has a default <a>text track text position alignment</a> which is defined
-      in terms of the value of the <a>text track cue text alignment</a>:</p>
+      <p>A <a>text track cue</a> has a <dfn>default text track cue text position alignment</dfn>
+      which is defined in terms of the value of the <a>text track cue text alignment</a>:</p>
 
       <ol>
 
@@ -1738,8 +1738,8 @@
   </ol>
 
   <p class="note">A <a>WebVTT size cue setting</a> configures
-  the size of the <a title="text track cue box">cue box</a> in the same direction as the <a>WebVTT text
-  position cue setting</a>. For horizontal cues, this is the width
+  the size of the <a title="text track cue box">cue box</a> in the same direction as the
+  <a>WebVTT text position cue setting</a>. For horizontal cues, this is the width
   of the <a title="text track cue box">cue box</a>. It is given as a percentage of the width of the
   frame.</p>
 
@@ -1750,20 +1750,34 @@
    <li><p>The string "<code title="">position</code>" as the <a>WebVTT cue setting name</a>.</p></li>
    <li><p>A U+003A COLON character (:).</p></li>
    <li>As the <a>WebVTT cue setting value</a>:
+   <ol>
+    <li>a position value consisting of:
     <ol>
      <li>One or more <a>ASCII digits</a>.</li>
      <li>A U+0025 PERCENT SIGN character (%).</li>
     </ol>
+    </li>
+    <li>an optional alignment value consisting of:
+    <ol>
+     <li>A U+002C COMMA character (,).</li>
+     <li>One of the following strings: <code title="">start</code>, <code title="">middle</code>,
+       <code title="">end</code></li>
+    </ol>
+    </li>
+   </ol>
    </li>
   </ol>
 
-  <p class="note">A <a>WebVTT text position cue setting</a>
-  configures the position of the text in the direction orthogonal to
+  <p class="note">A <a>WebVTT text position cue setting</a> configures the position of the
+  <a title="text track cue box">cue box</a> in the direction orthogonal to
   the <a>WebVTT line position cue setting</a>. For horizontal
-  cues, this is the horizontal position. The <a>WebVTT text
-  position cue setting</a> is given as a percentage, calculated
-  from the edge of the <a title="text track cue box">cue box</a> that the text begins (so for
-  left-to-right English text, the left edge).</p>
+  cues, this is the horizontal position. The text position is given as a percentage of the video frame.
+  The positioning is calculated relative to the <a title="text track cue text position start alignment">start</a>,
+  <a title="text track cue text position middle alignment">middle</a>, or
+  <a title="text track cue text position end alignment">end</a>
+  of the cue box, depending on the <a>default text track cue text position alignment</a> value, which is
+  overridden by the <a>WebVTT text position cue setting</a> alignment value.
+  </p>
 
   <p>A <dfn>WebVTT alignment cue setting</dfn> consists of the
   following components, in the order given:</p>