实现如下图的三列布局：

.box {
    width:1400px;
	margin:0 auto;
	padding-bottom:40px;
	> .left {
		float:left;
		width:180px;
		margin-top:100px;
		text-align:center;
	}
    > .center {
    	float:left;
    	margin-top:100px;
    	margin-left:130px;
    	item-box {
    	  float:left;
    	  text-align:left;
    	  margin-right:90px;
    	}
    }
    .right {
    	float:right;
    	margin-top:100px;
    }
}
注意：
// 最外层的box壳子上要加去除浮动的样式
.clearfix :after{
	content:'';
	display:block;
	height:0;
	clear:both;
	visibility:hidden;
}