.fo:after{content:".";display:block;height:0;clear:both;visibility:hidden;}
.fo{display:inline-block;/* Hides from IE-mac \*/}
* html .fo{height:1%;}
.fo{display:block;/* End hide from IE-mac */}
在指定的层 套用 class="fo" 即可，经高人简化，得：
.fo{zoom:1}
.fo:after{content:'\20';display:block;clear:both}