title: webkit-transition for "top" and "bottom" properties
body: <p>I'd like to make a css animation where a div (centered on a screen using <em>top</em> and <em>bottom</em> properties) expands by setting <em>top</em> and <em>bottom</em> to 20px. </p>
  
  <p>Is it possible? When I try to make it happen with:</p>
  
  <blockquote>
  <pre><code>-webkit-transition-property: top, bottom;
  -webkit-transition-duration: 0.5s;
  </code></pre>
  </blockquote>
  
  <p>animation is not performed. Am I doing something wrong, or is it not supposed to work with these properties?</p>
  
  <p>P.S. I'm doing this for a Titanium desktop application, so only webkit matters...</p>