title: Vertical centring with :after pseudo-element not working
body: <p>I'm trying to vertically centre my <code>introWrap</code> container using the <code>:after</code> pseudo-element method (as described at the end of <a href="http://css-tricks.com/centering-in-the-unknown/" rel="nofollow">this article</a>). I've always applied this method without any problems, but I can't for my life seem to understand why it doesn't work in this case (<a href="http://jsfiddle.net/4yfru/2/" rel="nofollow">http://jsfiddle.net/4yfru/2/</a>).</p>
  
  <p>Right now the <code>introWrap</code> div is at the top, whilst it should really be in the center on the vertical axis. I tried replacing the <code>:after</code> pseudo-element with a <code>span</code>, and it worked perfectly. Something's fishy is going on here and I don't know what.</p>
  
  <p>Could any kind soul please help me out here?</p>