title: :before not showing when overflow is auto
body: <p>So I'm making this tumblr theme that uses the :before for icons, like this:</p>
  
  <pre><code>    /* Icons */
      ol#posts li:before{
          content:"";
          display:block;
          position:absolute;
          left:-46px;
          width:32px;
          height:24px;
          background-repeat:no-repeat;
          // tried: overflow:visible;
      }
      li.text:before{
          background:url('http://i.imgur.com/z5YtE.png');
      }
      [...]
  </code></pre>
  
  <p>But when I set the overflow of li.post to auto, the icons won't show.</p>
  
  <pre><code>    li.post{
          position:relative;
          max-height:400px;
          overflow-x:auto;
      }
  </code></pre>
  
  <p>What's causing this and how can I fix it?</p>
  
  <p>Thank you :)</p>