before&&after

css用clearfix清除浮动实例 /*所有主流浏览器都支持 :after 伪元素。*/ /*.clearfix:after{content:”.”;display:block;height:0;clear:both;visibility:hidden} .clearfix{*+height:1%;}/*不知道有什么用处，不加ie7也没有问题*/ */.clearfix { *zoom: 1; } .clearfix:before, .clearfix:after { display: block; line-height: 0; content: “”; } .clearfix:after { clear: both; } .box{ background:#f00;width:500px; position:relative;} .l{float:left; background:#333;width:200px; height:100px;} .r{float:right;background:#666;width:200px; height:200px;opacity: 0.5;} .s{width:100px; height:100px;background:#999;position:absolute;right:-50px;;}

left

right

absolute