.top{height:100px;background:#ccc;}.main{height:600px;background:red;position:relative}.left{ height: 600px; width:200px; background: blue;? ? positive:absolute;top:0;left:0}.right{ height: 600px; width:100%; background: green; position:absolute; margin-left:210px; }.foot{height:50px;background:#F63;}