title: CSS expression to set height of div
body: <p>I want to set the height of a div based on CSS expression. </p>
  
  <p>Basically it should be set as some % (say 90%) of the viewport <strong>width</strong> 
  I tried the following, but is not working;</p>
  
  <pre><code>height:expression(document.documentElement.clientWidth ? document.documentElement.clientWidth : window.innerWidth );
  </code></pre>
  
  <p>I am looking at a cross-browser way of doing this (IE7+, FF4+, Safari)</p>