<div class="g-bd5 f-cb">
    <div class="g-sd51">
        <p class="red">左侧定宽</p>
    </div>
    <div class="g-mn5">
        <div class="g-mn5c">
            <p class="green">中间自适应</p>
        </div>
    </div>
    <div class="g-sd52">
        <p class="blue">右侧定宽</p>
    </div>
</div>

/*base布局块颜色*/
p{height: 150px; padding: 10px; color: #FFF;}
.red{background:red;}
.green{background:green;}
.blue{background:blue;}

/* 三列中间自适应布局 */
.g-bd5{margin:0 0 10px;}
.g-sd51,.g-sd52{position:relative;float:left;width:200px;margin:0 -200px 0 0;}
.g-sd52{float:right;width:160px;margin:0 0 0 -160px;}
.g-mn5{float:left;width:100%;}
.g-mn5c{margin:0 170px 0 210px;}