万能清除浮动样式

<style type="text/css">
.clearfix:after {
content: ".";
display: block;
height: 0;
clear: both;
visibility: hidden;
}
.clearfix {display: inline-block;}  /* for IE/Mac */
 
</style><!-- main stylesheet ends, CC with new stylesheet below... -->
 
<!--[if IE]>
<style type="text/css">
.clearfix {
zoom: 1;     /* triggers hasLayout */
<span style="color: #aa0000;">display: block;     /* resets display for IE/Win */</span>
}  /* Only IE can see inside the conditional comment
and read this CSS rule. Don't ever use a normal HTML
comment inside the CC or it will close prematurely. */
</style>
<![endif]-->

.clearfix:after {
    content: "020";
    display: block;
    height: 0;
    clear: both;
}
.clearfix {
    zoom: 1;
}

html body div.clear,
html body span.clear
{
     background: none;
     border: 0;
     clear: both;
     display: block;
     float: none;
     font-size: 0;
     margin: 0;
     padding: 0;
     overflow: hidden;
     visibility: hidden;
     width: 0;
     height: 0;
}