清除浮动

.clearfix:after, .container:after {
  content: "\0020";
  display: block;
  height: 0;
  clear: both;
  visibility: hidden;
  overflow:hidden;
}

/* Makes clearfix actually work in IE */
.clearfix, .container { display:inline-block; }
* html .clearfix,
* html .container { height:1%; }

对上面的代码还不是特别的明白 先马克

<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 */
    display: block;     /* resets display for IE/Win */
    }  /* 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]-->

最简单的方法

#outer 
{
background-color:#fff;
width:100%;	
overflow:auto;
}