网站导航用的div+css，但是不兼容ie浏览器，打开的时候比较混乱

公司网站改版，换了一个导航，大部分浏览器都显示正常，ie浏览器显示混乱，请大神帮我分析下#menu {margin:100px auto; display:block; height:38px; }#nav {display:block;}#nav .mainlevel {float:left; background:#2486c4; text-align:center; display:block; }#nav .mainlevel a {color:#fff; text-decoration:none; line-height:40px; height:40px; text-align:center; padding:0 20px; display:block;}#nav .mainlevel a:hover {color:#2486c4; text-decoration:none; background:white 0 0 repeat-x;}#nav .mainlevel ul {position:absolute; display:none; *width:2000px; }#nav .mainlevel li {float:left; background:#2486c4;}#nav .mainlevel li a {padding:0 12px; line-height:24px; height:24px; display:block; }#nav .mainlevel li a:hover {color:#2486c4; text-decoration:none; background:white 0 0 repeat-x;}#nav li a em {padding:0 3px;}.Triangle_con {height:9px; background:url(../image/bird.png) 36px 0 no-repeat; display:block; }这是css文件<div class="menu" > <ul id="nav"> <li class="mainlevel"><a href="#"> </a></li><li class="mainlevel"><a href="../news/xinweng.html">新闻中心</a></li> <li class="mainlevel"><a href="#">联系我们</a><ul class="sub_nav_01"> <span class="Triangle_con"></span> <li><a href="../womeng/jianjie.html">企业简介</a></li><li><a href="../zxzx/index.asp">在线留言</a></li></ul></li></ul></div>