清浮动

父级添加类别！

.clearfix{zoom:1;//兼容ie6,7}.clearfix:after{	content:".";	display: "block";	height: "0";	clear: both;	visibility: hidden;}

 

防止上下margin重叠，也可以清除浮动塌陷（推荐）

.clearfix:after,.clearfix:before{content:" ";display: table;}.clearfix:after{clear: both;}.clear{ clear:both;}