纯css做圆角

<style type="text/css">
.tab{position:relative;margin:20px auto; width:50px;text-align:center}
.tab a{ background:#F27B04;display:block;line-height:30px; height:30px;}
.tl,.tr{ background:#FFDEBB;display:block;width:1px; top:0;height:1px; position:absolute;}
.tl{left:0;}
.tr{right:0;}
</style>

<div class="tab">
	<a href="" rel="external nofollow" >试验</a>
	<b class="tl"></b>
	<b class="tr"></b>
</div>