div {
background:rgba(0,0,0,0.2) none repeat scroll !important; /*实现FF背景透明，文字不透明*/
background:#000; filter:Alpha(opacity=20);/*实现IE背景透明*/
width:500px;
height:500px;
color:#F30;
font-size:32px;
font-weight:bold;
}
div p { position:relative; }/*实现IE文字不透明*/