超级简单div上下左右居中

<style>
.juzhong {
	width:200px;
	height:200px;
	top:50%;
	left:50%;
	position:absolute;
}
.juzhong1 {
	width:200px;
	height:200px;
	background:#ccc;
	margin-left:-100px;
	margin-top:-100px;
	word-wrap:break-word;
}
</style>
<div class="juzhong"><!--外层div绝对定位，左上定点居中-->
	<div class="juzhong1"><!--内部div margin 负值纠正-->
	</div>
</div>