asp.net DIV+CSS盒子模型问题！！

<!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=utf-8" />
<title>无标题文档</title>
<style type="text/css">
div{-moz-box-sizing:border-box;-ms-box-sizing:border-box;box-sizing:border-box;}
.lef{background:#F00; border:2px solid #000; height:22px; float:left; width:50%;}
.min{background:#0F0; border:2px solid #000; height:22px; float:left; width:30%;}
.rig{background:#00F; border:2px solid #000; height:22px; float:left; width:20%;}
</style>
</head>
<body>
<div style=" width:700px;">
<div class="lef"></div><div class="min"></div><div class="rig"></div>
</div>
</body>
</html>IE6中不能排成一排，IE8中正常排成一排。高手指点！！！