jQuery $("body").height() returns undefined
<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>
