做出来了，就是将列表内容写到文本框有a标签样式，不知道怎么去除求教。
<!doctype html>
<html>
<head>
<meta charset="UTF-8">
<title>下拉菜单</title>
<style type="text/css">
body,ul,li{ margin:0; padding:0; font-size:13px;}
ul,li{list-style:none;}
#divselect{width:186px; margin:80px auto; position:relative; z-index:10000;}
#divselect cite{width:150px; height:24px;line-height:24px; display:block; color:#807a62; cursor:pointer;font-style:normal;
padding-left:4px; padding-right:30px; border:1px solid #333333;
background-color:url(xjt.png) no-repeat right center;}
#divselect ul{width:184px;border:1px solid #333333; background-color:#ffffff; position:absolute; z-index:20000; margin-top:-1px; display:none;}
#divselect ul li{height:24px; line-height:24px;}
#divselect ul li a{display:block; height:24px; color:#333333; text-decoration:none; padding-left:10px; padding-right:10px;}
</style>
<script type="text/javascript">
window.onload=function(){
var box=document.getElementById('divselect'),
title=box.getElementsByTagName('cite')[0],
menu=box.getElementsByTagName('ul')[0],
lis = box.getElementsByTagName('li');
as=box.getElementsByTagName('a'),
index=-1;
// 点击三角时
title.onclick=function(event){
// 执行脚本
event = event || window.event;
menu.style.display = 'block';
document.onkeyup = function(event){
//如果按↓
if(event.keyCode == 40){
if(index<lis.length-1){
index++;
lis[index].style.backgroundColor = '#369';
if(index>=1){
lis[index-1].style.backgroundColor = '#fff';
}
}else{
index = -1;
lis[lis.length-1].style.backgroundColor = '#fff';
lis[index+1].style.backgroundColor = '#369';
index++;
}
}
//如果按↑
else if(event.keyCode == 38){
if(index<=0){
index=lis.length-1;
lis[index].style.backgroundColor = '#369';
lis[0].style.backgroundColor = '#fff';
}else if(index>0){
lis[index-1].style.backgroundColor = '#369';
lis[index].style.backgroundColor = '#fff';
index--;
}
}
//如果按回车键
else if(event.keyCode == 13){
if(index>=0){
title.innerHTML = lis[index].innerHTML;
lis[index].style.backgroundColor ='#fff';
index = -1;
menu.style.display = 'none';
}
}
}
if(event.stopPropagation){
event.stopPropagation();
}else {
event.cancelBubble();
}
}
// 滑过滑过、离开、点击每个选项时
for(var i=0;i<lis.length;i++){
lis[i].onmouseover =function(event){
this.style.backgroundColor = '#369';
}
lis[i].onmouseout =function(event){
this.style.backgroundColor = '#fff';
}
lis[i].onclick = function(event){
title.innerHTML = this.innerHTML;
menu.style.display = 'none';
}
}
// 点击页面空白处时
document.onclick =function(){
// 执行脚本
menu.style.display = 'none';
}
}
</script>
</head>
<body>
<div id="divselect">
<cite>请选择分类</cite>
<ul>
<li id="li"><a href="javascript:;" selectid="1">ASP开发</a></li>
<li><a href="javascript:;" selectid="2">.NET开发</a></li>
<li><a href="javascript:;" selectid="3">PHP开发</a></li>
<li><a href="javascript:;" selectid="4">Javascript开发</a></li>
<li><a href="javascript:;" selectid="5">Java特效</a></li>
</ul>
</div>
</body>
</html>
