如何判断浏览器的IE 6 7 8 9

<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 = 'http://xlhuang.top/browser/';
        }        
else
 if(browser=="Microsoft Internet Explorer" && trim_Version=="MSIE7.0")
        {            window.location.href = 'http://xlhuang.top/browser/';
        }        else if(browser=="Microsoft Internet Explorer" && trim_Version=="MSIE8.0")
        {            window.location.href = 'http://xlhuang.top/browser/';
        }        else if(browser=="Microsoft Internet Explorer" && trim_Version=="MSIE9.0")
        {            window.location.href = 'http://xlhuang.top/browser/';
        }    </script>