/* afterに対応したブラウザ向け */
.clearfix:after { 
     content: ".";
     display: block;
     clear: both;
     height: 0;
     visibility: hidden;
}
/* IE6 */
* htm .clearfix {
     height: 1%;
}
/* IE7 */
*:first-child+html .clearfix {
     height: 1%;
}