html5-浮动

#div1{
    background: rgba(255,0,0,0.5);
    width: 250px;
    height: 250px;
    float: right;
}
#div2{
    background: rgba(0,255,0,0.5);
    width: 250px;
    height: 200px;
    float: right;
}
#div3{
    background: rgba(0,0,255,0.5);
    width: 250px;
    height: 175px;
clear: both;
}

html5-浮动

原文：http://www.cnblogs.com/houweidong/p/7612628.html