title: jQuery $("body").height() returns undefined
body: <p>I have a call like this:</p>
  
  <pre><code>$("#ContextMenuModal").height($("body").height());
  </code></pre>
  
  <p>However <code>$("body").height()</code> returns undefined when I view it in Firebug.</p>
  
  <p>What would cause jQuery to return undefined for the body height?</p>
  
  <p>I am using jQuery 1.4.1.</p>
  
  <p>Edit:</p>
  
  <p>This is inside an iFrame</p>