css控制元件的显示隐藏

<style>
　#links{margin: 0; padding: 0; float: left; width: 125px;}
　#links a{text-decoration: none; display: block; color: black; font-size: 12px;}
　#links a:hover{color: #f00; background: #eee; border-right: 5px double black;}
　#links a span{display: none;}
　#links a:hover span{display: block; position: absolute; top: 50; left: 0; width:125px; padding: 5px; margin: 10px; z-index: 100; color: #aaa; background: #000; font-size: 12px;}
　</style>
　<div id="links"><a href="#">links<span>move there</span></a></div>