<style type="text/css">
.miao{width:170px;height:100px;display:table;text-align:center;border:solid 1px red;}
.miao span{display:table-cell;vertical-align:middle;border:solid 1px blue;}
.miao span img{border:dashed 1px green;}
</style>

<style type="text/css">
.miao{position:relative;overflow:hidden;}
.miao span{position:absolute;left:50%;top:50%;}
.miao span img{position:relative;left:-50%;top:-50%;}
</style>



<div class="miao" style="width:500px;height:220px;">
    <span><img src="http://www.google.cn/intl/zh-CN/images/logo_cn.gif" alt="Google" /></span>
</div>