Well, 100% works if you want the height of the browser window, not the height of the page 
Code:
<html>
<head>
<style>
#div1
{
background-color: #ff0000;
position: absolute;
left: 0px;
top: 0px;
width: 300px;
}
#div2
{
background-color: #00ff00;
position: absolute;
left: 300px;
top: 0px;
width: 300px;
}
</style>
<script language="javascript">
function setHeight()
{
var div1 = document.getElementById("div1");
var div2 = document.getElementById("div2");
div1.style.height = div2.offsetHeight;
}
</script>
</head>
<body onload="setHeight()">
<div id="div1">
A shorter text.
</div>
<div id="div2">
A long text causing scrollbars. A long text ... causing scrollbars.
</div>
</body>
</html>
Bookmarks