clearfix清除浮動

 clearfix定義如下：

<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：子節點設定了浮動，在其父節點上加入clearfix類別便可達到清除浮動效果

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