fix forms typo on error state

docs/base-css.html

@@ -1059,7 +1059,7 @@ For example, <code>section</code> should be wrapped as inline.
       <p>Bootstrap features styles for browser-supported focused and <code>disabled</code> states. We remove the default Webkit <code>outline</code> and apply a <code>box-shadow</code> in it's place for <code>:focus</code>.</p>
       <hr>
       <h3>Form validation</h3>
-      <p>It also includes validation styles for errors, warnings, and success. To use, add the a class to the surrounding <code>.control-group</code>.</p>
+      <p>It also includes validation styles for errors, warnings, and success. To use, add the error class to the surrounding <code>.control-group</code>.</p>
 <pre class="prettyprint linenums">
 &lt;fieldset
   class="control-group error"&gt;

docs/templates/pages/base-css.mustache

@@ -983,7 +983,7 @@
       <p>{{_i}}Bootstrap features styles for browser-supported focused and <code>disabled</code> states. We remove the default Webkit <code>outline</code> and apply a <code>box-shadow</code> in it's place for <code>:focus</code>.{{/i}}</p>
       <hr>
       <h3>{{_i}}Form validation{{/i}}</h3>
-      <p>{{_i}}It also includes validation styles for errors, warnings, and success. To use, add the a class to the surrounding <code>.control-group</code>.{{/i}}</p>
+      <p>{{_i}}It also includes validation styles for errors, warnings, and success. To use, add the error class to the surrounding <code>.control-group</code>.{{/i}}</p>
 <pre class="prettyprint linenums">
 &lt;fieldset
   class="control-group error"&gt;