port docs fix from 2.3.0-wip to new css page

docs/css.html

@@ -1281,6 +1281,7 @@ For example, <code><section></code> should be wrapped
 
           <h3 id="forms-invalid-inputs">Invalid inputs</h3>
           <p>Style inputs via default browser functionality with <code>:invalid</code>. Specify a <code>type</code>, add the <code>required</code> attribute if the field is not optional, and (if applicable) specify a <code>pattern</code>.</p>
+          <p>This is not available in versions of Internet Explorer 7-9 due to lack of support for CSS pseudo selectors.</p>
           <form class="bs-docs-example form-inline">
             <input class="span3" type="email" placeholder="test@example.com" required>
           </form>

docs/templates/pages/css.mustache

@@ -1221,6 +1221,7 @@ For example, <code><section></code> should be wrapped
 
           <h3 id="forms-invalid-inputs">Invalid inputs</h3>
           <p>Style inputs via default browser functionality with <code>:invalid</code>. Specify a <code>type</code>, add the <code>required</code> attribute if the field is not optional, and (if applicable) specify a <code>pattern</code>.</p>
+          <p>This is not available in versions of Internet Explorer 7-9 due to lack of support for CSS pseudo selectors.</p>
           <form class="bs-docs-example form-inline">
             <input class="span3" type="email" placeholder="test@example.com" required>
           </form>