title: Bootstrap fixed navbar inside div
body: <p>In <a href="http://twitter.github.com/bootstrap/components.html#navbar" rel="noreferrer">bootstrap documentation</a> they're able to "trap" a <code>.navbar-fixed-top</code> inside their <code>.bs-docs-example</code> div:</p>
  
  <pre><code>&lt;div class="bs-docs-example bs-navbar-top-example"&gt;
      &lt;div class="navbar navbar-fixed-top" style="position: absolute;"&gt;
          &lt;div class="navbar-inner"&gt;
          [...]
  </code></pre>
  
  <p>But if I do the same in my test page the navbar "escapes" the div and get fixed in the top of the body, not the top of the div. How it's the trick achieved?</p>