CSS自适应宽度圆角按钮

<style>

a{background:url(http://5key.net/demo/liquid-css-menu/1.gif) left 0; color:#fff; text-decoration:none; height:30px; float:left; cursor:hand; margin:0 5px 0 0;}

#aa a:hover{background:url(http://5key.net/demo/liquid-css-menu/1.gif) left -30px;height:30px;}

#aa a span{background:url(http://5key.net/demo/liquid-css-menu/1.gif) right 0; padding:9px 8px 5px 0; margin:0 0 0 8px; float:left; height:16px;}

#aa a:hover span{background:url(http://5key.net/demo/liquid-css-menu/1.gif) right -30px; color:#000; padding:9px 8px 5px 0; margin:0 0 0 8px; height:16px; }

</style>

<div ><span>好了，就这样把。别扯了~</span></a>

</div>