DIV 上下左右居中黑科技

<style> 
#info{height:0px; width:0px;top:50%; left:50%;position:absolute;} 
#center{background:#FFCC33;border:1px solid #0033FF; width:300px;height:300px;position:absolute; margin:-150px;} 
</style> 
<div id="info"> 
<div id="center">哆啦A梦，起床啦！</div> 
</div>