div 宽高相等2种实现方式

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%;
}