title: Twitter Bootstrap Affixed Navbar - div below jumps up
body: <p>Rather hard to describe the problem. So just look at this jsFiddle:</p>
  
  <p><a href="http://jsfiddle.net/xE2m7/" rel="noreferrer">http://jsfiddle.net/xE2m7/</a></p>
  
  <p>When the navbar gets fixed to the top the content jumps below it.</p>
  
  <p>CSS:</p>
  
  <pre><code>.affix {
      position: fixed;
      top: 0px;
  }
  #above-top {
      height: 100px;
      background: black;
  }
  </code></pre>
  
  <p>Where is the problem?</p>