圣杯布局

    .left,
    .middle,
    .right{ 
        position: relative;
        float: left;
        height: 500px;
    }
    .container{
        padding:0 200px 0 200px;
        overflow: hidden;
    }
    .left{
        margin-left: -100%;
        left: -200px;
        width: 200px;
    }
    .right{
        margin-left: -200px;
        right: -200px;
        width: 200px;
    }
    .middle{ 
        width: 100%;
    }