div布局整理
======================上下两行四个区域布局=====================

其中:div{border:0px;margin:0px;}<div style="clear:both;width:100%;">   <div style="width:50%;float:left;">left1</div>   <div style="width:50%;float:right;">right1</div></div><div style="clear:both;width:100%;">   <div style="width:50%;float:left;">left2</div>   <div style="width:50%;float:right;">right2</div></div>