IE6对widthCliennt不起作用

为什么IE6对widthCliennt无效，看源码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>ClientWidth</title>
</head>
<body>
<div id="demo" style="width:300px;border:1px solid red;">
<table width="500">
<tr><td>aaaaaaaaaaaaaaaa</td></tr>
</table>
</div>
<script type="text/javascript">
(function(obj,offset){
       for(var i=0;i<document.getElementById(obj).getElementsByTagName("*").length;i++){
              if(document.getElementById(obj).getElementsByTagName("*")[i].clientWidth>document.getElementById(obj).clientWidth){
                            document.getElementById(obj).getElementsByTagName("*")[i].style.width=(document.getElementById(obj).clientWidth-offset)+"px";
                     }
       }
}("demo",10))
</script>
</body>
</html>
在IE6中table会把div的宽度称大？