fix spelling error

Author: John Daggett

css3-fonts/Fonts.html

@@ -1875,7 +1875,7 @@ <h3 id=font-synthesis-prop><span class=secno>3.8 </span>Controlling
    disallows all synthetic faces.
 
   <div class=example>
-   <p>The style rule below diables the use of synthetically obliqued Arabic:</p>
+   <p>The style rule below disables the use of synthetically obliqued Arabic:</p>
 
    <pre>*:lang(ar) { font-synthesis: none; }
 </pre>