判断IE浏览器的版本问题

<script type="text/javascript"> 
var browser=navigator.appName 
var b_version=navigator.appVersion 
var version=b_version.split(";"); 
var trim_Version=version[1].replace(/[ ]/g,""); 
if(browser=="Microsoft Internet Explorer" && trim_Version=="MSIE6.0") 
{ 
    window.location.href = location.href + 'UpdateBrowser.html';
} 
else if(browser=="Microsoft Internet Explorer" && trim_Version=="MSIE7.0") 
{ 
    window.location.href = location.href + 'UpdateBrowser.html';
} 
else if(browser=="Microsoft Internet Explorer" && trim_Version=="MSIE8.0") 
{ 
    window.location.href = location.href + 'UpdateBrowser.html';
} 
else if(browser=="Microsoft Internet Explorer" && trim_Version=="MSIE9.0") 
{ 
    window.location.href = location.href + 'UpdateBrowser.html';
} 
</script>