clearfix清除浮动

 clearfix定义如下：

<span style="color: #800000;">.clearfix:after</span>{<span style="color: #ff0000;">visibility</span>:<span style="color: #0000ff;">hidden</span>;<span style="color: #ff0000;">display</span>:<span style="color: #0000ff;">block</span>;<span style="color: #ff0000;">font-size</span>:<span style="color: #0000ff;">0</span>;<span style="color: #ff0000;">content</span>:<span style="color: #0000ff;"> ” “</span>;<span style="color: #ff0000;">clear</span>:<span style="color: #0000ff;">both</span>;<span style="color: #ff0000;">height</span>:<span style="color: #0000ff;">0</span>;}<span style="color: #800000;">
.clearfix</span>{<span style="color: #ff0000;">*zoom</span>:<span style="color: #0000ff;">1</span>;}

方法：子节点设置了浮动，在其父节点上添加clearfix类便可达到清除浮动效果

参考：http://blog.sina.com.cn/s/blog_60b35e830101c1r8.html