title: z-Index behaviour on pseudo elements
body: <p>see:</p>
  <p><a href="http://jsfiddle.net/Kq2PY/" rel="nofollow noreferrer">http://jsfiddle.net/Kq2PY/</a></p>
  <p>the div is relative with z-index 5, and the :after thing is absolute with z-index 2.</p>
  <p>So shouldn't :after be behind the div?</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>div{
      position:relative;
      z-index: 5;
      background: #000;
      padding: 10px;
  }    
  
  div:after{
      content: '';
      position: absolute;
      z-index: 2;            /*  &lt;= not working:( */
      background: #3d3;
      left: 20px;
      top: 20px; 
      width: 30px;
      height: 30px;
  }    </code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div&gt;erferf&lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>