javascript判断IE浏览器的版本

<script language="javascript">
function ie(){
var isIE=!!window.ActiveXObject;
var isIE6=isIE&&!window.XMLHttpRequest;
var isIE8=isIE&&!!document.documentMode;
var isIE7=isIE&&!isIE6&&!isIE8;
if (isIE)
{
   if (isIE6){
   var style = document.createElement(\'link\');
   style.href = \'/static/skins/ie7/skinIE6.css\';
   style.rel = \'stylesheet\';
style.type = \'text/css\';
document.getElementsByTagName(\'HEAD\').item(0).appendChild(style);
alert("ie6");
   }
else if (isIE8)
   {
   var style = document.createElement(\'link\');
   style.href = \'/static/skins/ie7/skinIE7.css\';
   style.rel = \'stylesheet\';
style.type = \'text/css\';
document.getElementsByTagName(\'HEAD\').item(0).appendChild(style);
alert("ie8");
    }
else if (isIE7)
   {
    var style = document.createElement(\'link\');
   style.href = \'/static/skins/ie7/skinIE7.css\';
   style.rel = \'stylesheet\';
style.type = \'text/css\';
document.getElementsByTagName(\'HEAD\').item(0).appendChild(style);
alert("ie7");
}
}

}

//第一次页面的加载时候调用事件
if (window.addEventListener)
    {
        window.addEventListener("load", ie, false);
    }
else if (window.attachEvent)
{
        window.attachEvent("onload", ie);
    }
else{
        window.onload=ie;
}
</script>