ie8以下

 if(!+[1,])  

 if(window.attachEvent){ alert("ie")}else if(window.addEventListener){alert("not ie")}else{alert("不支持DHTML")}

ie6

 if(document.all)

ie浏览器  !ie 浏览器

var navigatorName = "Microsoft Internet Explorer"; 
var isIE = false; 
if( navigator.appName == navigatorName ){ 
isIE = true; 
alert("ie") 
}else{
alert("not ie") 
}