fixes #13356: clarify use of clearfix on parents

docs/_includes/css/helpers.html

@@ -116,7 +116,7 @@
 
 
   <h3 id="helper-classes-clearfix">Clearfix</h3>
-  <p>Clear the <code>float</code> on any element with the <code>.clearfix</code> class. Utilizes <a href="http://nicolasgallagher.com/micro-clearfix-hack/">the micro clearfix</a> as popularized by Nicolas Gallagher. Can also be used as a mixin.</p>
+  <p>Easily clear <code>float</code>s by adding <code>.clearfix</code> <strong>to the parent element</strong>. Utilizes <a href="http://nicolasgallagher.com/micro-clearfix-hack/">the micro clearfix</a> as popularized by Nicolas Gallagher. Can also be used as a mixin.</p>
 {% highlight html %}
 <!-- Usage as a class -->
 <div class="clearfix">...</div>