ie7 样式问题求解答

代码
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>主页</title>
<meta name="keywords" content="主页" />
<meta name="description" content="主页" />
<style>
*{
margin: 0;
padding: 0;
border: 0;
}
ol, ul ,li{
list-style: none;
}
img {
border: 0;
vertical-align:middle;
}
body{
color:#000000;
background:#fff;
}
#footer{
width: 1024px;
margin: 0 auto;
overflow: hidden;
z-index: 1000;
position: fixed!important;
bottom:0!important;
}
#footer ul{
width: 100%;
overflow: hidden;
}
.navi_style_01{
float: left;
width: 70px;
height: 54px;
line-height: 54px;
background-color: #11aeff;
/*background-image: url(../images/line-blue-blue.png);
background-repeat: no-repeat;
background-position:left -1px;*/
color: white;
text-align: center;
padding-left: 30px;
cursor: pointer;
}
.li_top{
margin-top: 26px;
}
.navi_style_02{
background-color: #11aeff;
/*background-image: url(../images/line-white-blue.png);*/
color: white;
}
.navi_style_03{
width: 394px;
height: 80px;
line-height: 80px;
background-color: #282828;
/*background-image: url(../images/line-black.png);*/
color: white;
font-size: 14px;
}
</style>
</head>
<body>
<div id="main_page">
<div id="footer">
<ul>
<li><div class="navi_style_01 li_top navi_style_02">首页</div></li>
<li><div class="navi_style_01 li_top ">新闻动态</div></li>
<li><div class="navi_style_01 li_top ">成功案例</div></li>
<li><div class="navi_style_01 li_top">UI展示</div></li>
<li><div class="navi_style_01 li_top">关于我们</div></li>
<li><div class="navi_style_01 li_top">相关下载</div></li>
<li><div class="navi_style_01 navi_style_03">XXX有限公司 Copyright <span style="font-size:20px;">©</span> 2008-2012</div></li>
</ul>
</div>
</div>
</body>
</html>
如上IE8 IE9可以正常显示，但是IE7会错乱，调试查看是offsetTop的大小逐步变大了，求解决方案~~~