判断是不是IE6，如果是则提示升级浏览器 _Web前端

判断是否IE6，如果是则提示升级浏览器
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta http-equiv="MSThemeCompatible" content="no" />
<title></title>
<style type="text/css"> 
#ie6-warning{ 
	background:rgb(255,255,225) url("http://dl.iteye.com/upload/attachment/474608/b47ae4df-5c3a-39b4-b620-0de68fa5904a.gif") no-repeat scroll 3px center; 
	position:absolute; 
	top:0; 
	left:0; 
	font-size:12px; 
	color:#333; 
	width:97%; 
	padding: 2px 15px 2px 23px; 
	text-align:center; 
} 
#ie6-warning a { 
	text-decoration:none; 
} 
</style> 

</head>
<body>
<!--[if lte IE 6]> 
<div id="ie6-warning">您正在使用 Internet Explorer 6，在本页面的显示效果可能有差异。建议您升级到 <a href="http://www.microsoft.com/china/windows/internet-explorer/" target="_blank">Internet Explorer 8</a> 或以下浏览器： <a href="http://www.mozillaonline.com/">Firefox</a>
</div> 
<script type="text/javascript"> 
function position_fixed(el, eltop, elleft){ 
// check if this is IE6 
if(!window.XMLHttpRequest) 
window.onscroll = function(){ 
el.style.top = (document.documentElement.scrollTop + eltop)+"px"; 
el.style.left = (document.documentElement.scrollLeft + elleft)+"px"; 
} 
else el.style.position = "fixed"; 
} 
position_fixed(document.getElementById("ie6-warning"),0, 0); 
</script> 
<![endif]--> 
</body>
</html>