title: :last-child does not select the last element
body: <p>I want to remove the background from the last <code>figure</code> element:</p>
  
  <pre><code>@media (min-width: 50em) {
    #mission #press figure {
      padding-left: 0;
      background: url('/assets/img/splash-green.png?1345829368') no-repeat 50% bottom;
    }
    #mission #press figure:last-child {
      background: none;
    }
  }
  </code></pre>
  
  <p>The background still shows up. Am I mis-targeting?</p>