Here is a working css, tested under Firefox / IE7 / Safari / Chrome / Opera.
* {margin:0px;padding:0px;overflow:hidden}
div {position:absolute}
div#header {top:0px;left:0px;right:0px;height:60px}
div#wrapper {top:60px;left:0px;right:0px;bottom:0px;}
div#left {top:0px;bottom:0px;left:0px;width:50%;overflow-y:auto}
div#right {top:0px;bottom:0px;right:0px;width:50%;overflow-y:auto}
"overflow-y" is not w3c-approved, but every major browser supports it. Your two divs #left and #right will display a vertical scrollbar if their content is too high.
For this to work under IE7, you have to trigger the standards-compliant mode by adding a DOCTYPE :
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title></title>
<style type="text/css">
*{margin:0px;padding:0px;overflow:hidden}
div{position:absolute}
div#header{top:0px;left:0px;right:0px;height:60px}
div#wrapper{top:60px;left:0px;right:0px;bottom:0px;}
div#left{top:0px;bottom:0px;left:0px;width:50%;overflow-y:auto}
div#right{top:0px;bottom:0px;right:0px;width:50%;overflow-y:auto}
</style>
</head>
<body>
<div id="header"></div>
<div id="wrapper">
<div id="left"><div style="height:1000px">high content</div></div>
<div id="right"></div>
</div>
</body>