css 水平垂直居中

<style type="text/css">

   div{ border:1px solid #ccc; height:500px; width:500px; text-align:center; margin:0 auto; background:#ccc;}

   img{ vertical-align:middle; }

   div span{ height:100%; width:0; overflow:hidden; display:inline-block; vertical-align:middle; }

</style>

<div class="test">

<img src="icon.png"><span> </span>

</div>