小图标垂直居中

<style type="text/css">
.content{
width:20%;
height:60px;
border:1px solid red;
text-align:center;}
span{
height:100%;
vertical-align:middle;
line-height:30px;}
img{
vertical-align:middle;}
</style>
<div class="content">
<img src="icon.jpg">
<span>测试一下吧</span>
</div>