我输入老师的代码显示的中间一列没顶格啊，而且中间一列与两边还有空隙。？？？？
<style type="text/css">
.body{margin:0; padding:0;}
.left{ width:200px; height:500px; background:#30C; position:absolute; left:0; top:0;}
.middle{height:500px; background:#F00; margin:0 300px 0 200px;}
.right{ width:300px; height:500px; background:#FC0; position:absolute; right:0; top:0;}
</style>
</head>
<body>
<div class="left">456</div>
<div class="middle">987</div>
<div class="right">321</div>
</div>
</body>
</html>
