Fixes #6808: mention IE lame-itude in docs for invalid inputs

docs/base-css.html

@@ -1585,6 +1585,7 @@ For example, <code><section></code> should be wrapped
 
           <h3>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/base-css.mustache

@@ -1522,6 +1522,7 @@
 
           <h3>{{_i}}Invalid inputs{{/i}}</h3>
           <p>{{_i}}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>.{{/i}}</p>
+          <p>{{_i}}This is not available in versions of Internet Explorer 7-9 due to lack of support for CSS pseudo selectors.{{/i}}</p>
           <form class="bs-docs-example form-inline">
             <input class="span3" type="email" placeholder="test@example.com" required>
           </form>