请问我想写一个下拉菜单，用css写 当移动上去的时候显示吗，离开时候隐藏，请教高手……

<style type="text/css">
<!--
body,td,th {
 font-family: Verdana, Geneva, sans-serif;
 font-size: 100%;
 color: #666;
}
body {
 background-color: #fff;
 margin-left: 20px;
 margin-top: 20px;
 margin-right: 20px;
 margin-bottom: 20px;
}
 
a, a:hover, a:active, a:focus {
 outline:0;
 direction:ltr;
}
 
.wrapper {
 position:relative; height:25px;
}
 
.mainmenu {
 position:absolute;
 z-index:100;
 font-family:Verdana, Geneva, sans-serif;
 font-weight:normal;
 font-size:90%;
 line-height:25px;
 left:50%;
 margin-left:-303px;
 width:606px;
}
 
ul.menu {
 padding:0;
 margin:0;
 list-style:none;
 width:100px;
 overflow:hidden;
 float:left;
 margin-right:1px;
}
 
ul.menu a {
 text-decoration:none;
 color:#fff;
 padding-left:5px;
}
 
ul.menu li.list {
float:left;
width:250px;
margin:-32767px -125px 0px 0px;
background:url(images/top1.png) no-repeat left bottom;
}
 
ul.menu li.list a.category {
position:relative;
z-index:50;
display:block;
float:left;
width:120px;
margin-top:32767px;
background:transparent;
}
 
ul.menu li.list a.category:hover,
ul.menu li.list a.category:focus,
ul.menu li.list a.category:active {
 margin-right:1px;
 background-image:url(images/tophover1.png);
 background-repeat:no-repeat;
 background-position:left top;
}
 
ul.submenu {
 float:left;
 padding:25px 0px 0px 0px;
 margin:0;
 list-style:none;
 background-image:url(images/tophover1.png);
 background-repeat:no-repeat;
 background-position:left top;
 margin:-25px 0px 0px 0px;
}
 
ul.submenu li a {
float:left;
width:120px;
background:#369;
clear:left;
}
 
ul.submenu li a.endlist {
 background:url(images/bottom1.png);
}
 
ul.submenu li a.endlist:hover,
ul.submenu li a.endlist:focus,
ul.submenu li a.endlist:active {
background:url(images/bottomhover1.png);
}
 
ul.submenu a:hover,
ul.submenu a:focus,
ul.submenu a:active {
background:#900;
margin-right:1px;
}
-->
 
 
</style>
 
 
<div class="wrapper">
<div class="mainmenu">
<ul class="menu">
<li class="list">
 <a class="category" href="#Home">Home</a>
</li>
</ul>
<ul class="menu">
<li class="list">
 <a class="category" href="#about">About Us&nbsp;&nbsp;&raquo;</a>
 <ul class="submenu">
  <li><a href="#about1">About link 1</a></li>
  <li><a href="#about2">About link 2</a></li>
  <li><a href="#about3">About link 3</a></li>
        <li><a href="#about4">About link 4</a></li>
  <li><a class="endlist" href="#about5">About link 5</a></li>
 </ul>
</li>
</ul>
<ul class="menu">
<li class="list">
 <a class="category" href="#articles">Articles&nbsp;&nbsp;&raquo;</a>
 <ul class="submenu">
  <li><a href="#articles1">Articles link 1</a></li>
  <li><a href="#articles2">Articles link 2</a></li>
  <li><a href="#articles3">Articles link 3</a></li>
  <li><a class="endlist" href="#articles4">Articles link 4</a></li>
 </ul>
</li>
</ul>
<ul class="menu">
<li class="list">
 <a class="category" href="#news">News&nbsp;&nbsp;&raquo;</a>
 <ul class="submenu">
  <li><a href="#news1">News link 1</a></li>
  <li><a href="#news2">News link 2</a></li>
  <li><a class="endlist" href="#news3">News link 3</a></li>
 </ul>
</li>
</ul>
<ul class="menu">
<li class="list">
 <a class="category" href="#donate">Donate</a>
</li>
</ul>
<ul class="menu">
<li class="list">
 <a class="category" href="#contact">Contact</a>
</li>
</ul>
<!-- end mainmenu --></div>
<!-- end wrapper --></div>


试试可以不

非常感谢…………