看看怎么用 background-position 解决这个问题，实现快速"切换"，这里只用到一张图片
至于代码中的font:10px/1也是不常见的用法
可以参考这里:http://www.w3.org/Style/CSS/Test/CSS1/current/sec5526c.htm
这种用法放在网站地图或者导航条上的效果：
<style type="text/css">
#menu a {
display:block;
width:150px;
margin:6px;
padding:10px 0 10px 32px;
font:10px/1 sans-serif;
color:#f90;
background: url("http://webdesign.chinaitlab.com/UploadFiles_8014/200707/20070707163826262.gif?http://www.xvna.com") top left no-repeat;
text-decoration: none;
}
#menu a:hover {
background-position: 0 -39px;
color:red;
}
#menu a:active {
background: url("http://webdesign.chinaitlab.com/UploadFiles_8014/200707/20070707163826262.gif?http://www.xvna.com") 0 -78px no-repeat;
color:black;
}
</style>
</head>
<body>
<div id="menu">
<a href="###">Menu link 1</a>
<a href="###">Menu link 2</a>
<a href="###">Menu link 3</a>
<a href="###">Menu link 4</a>
<a href="###">Menu link 5</a>
</div><script language="Javascript">
var now = new Date();
document.write("<img src='http://counter.yesky.com/counter.shtml?CID=54197&AID=-1&refer="+escape(document.referrer)+"&rand="+ now.getTime() + "&cur="+escape(document.URL)+"' border='0' alt='' width='0' height='0'>");
</script>
<noscript>
<img src="http://counter.yesky.com/counter.shtml?CID=54197&AID=-1&refer=noscriptcounter&cur=noscriptcounter" border='0' width='0' height='0'/>
</noscript>