<html>
<!-- This page is loaded in a 200px-square iframe scrolled to #down. -->
<body>
<div id="first" style="height: 150px; background: lightblue;">first</div>
<div id="down" style="height: 250px; background: lightgreen;">second</div>
<script>document.documentElement.offsetWidth;</script>
</body>
</html>
