.body.scrollHeight doesn't work in Firefox
<p><code>.body.scrollHeight</code> does not work in Firefox.</p>

<p>See: <a href="http://jsfiddle.net/gjrowe/X63KR/" rel="nofollow">http://jsfiddle.net/gjrowe/X63KR/</a></p>

<p>What is the correct syntax to use instead?</p>
