title: top: 0px; bottom: 0px; doesn't work as expected
body: <p>Why doesn't the following display a 200px-high blue block?</p>
  
  <pre><code>&lt;div style="position: absolute; height: 500px;"&gt;
      &lt;div style="width: 200px; height: 300px; background-color: Green; position: relative;"&gt;
          a&lt;/div&gt;
      &lt;div style="width: 200px; background-color: Blue; top: 0px; bottom: 0px; position: relative;"&gt;
          b&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>