div.wh{
background:#ff0;width:50%;position:relative;display:inline-block;
}
div.wh:before{
content: "";
display: inline-block;
padding-bottom: 100%;
width: .1px;
vertical-align: middle;
}
div.wh{
background:#ff0;
display:inline-block;
width:50%;
padding-bottom: 50%;
}
原文：http://www.cnblogs.com/cyhj/p/5783431.html