<style type="text/css">
ul, li{list-style:none; padding:0; margin:0; line-height:160%}
a{font:normal 14px "宋体"; text-decoration:none}
li.mainnav{margin:10px; border:1px solid #039; float:left}
.mainnav ul{display:none}
.mainnav:hover ul, .mainnav:hover li{display:block}
.mainnav:hover{z-index:2; background:#fff}
</style>
<div style="position:relative; width:600px; height:40px">
<div style="position:absolu