<div class="XXX">
<div class="ss"></div>
<div class="clearfix"></div>/*最后一个元素后面加上*/
</div>
清楚浮动的样式
/* clear */
.clearfix:after {content: "\20";display: block;height: 0;clear: both;visibility: hidden;}
.clearfix {*zoom:1;display: inline-block;clear: both;}
.clearfix {display: block;}
.clear{clear:both;}