Фегня. На.
Код:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Untitled</title>
<style type="text/css">
#left{float:left;width:50%;margin-right:-150px;}
#left .indent{margin-right:160px;border:1px solid #000;background:#ccc;padding:1em;}
#right{float:right;width:50%;_width:49.9%;margin-left:-150px;}
#right .indent{margin-left:160px;border:1px solid #000;background:#ccc;padding:1em;}
#center{float:left;width:300px;}
#center .indent{border:1px solid #000;background:#ccc;padding:1em;}
</style>
</head>
<body><script type="text/javascript"></script>
<div id="main">
<div id="left"><div class="indent">left</div></div>
<div id="center"><div class="indent">center</div></div>
<div id="right"><div class="indent">right</div>
</div>
</body>
</html>