var Class = {
 create: function() {
   return function() {
     this.initialize.apply(this, arguments);
   }
 }
}


var StyleClass = Class.create();
StyleClass.prototype = {
 initialize:function(dir){
   this._dir = dir ? dir : "";
 },
 
 styleWrite:function(url){
   if(url.length < 5) return false;
   url = this._dir + url;
   document.write('<link rel="stylesheet" type="text/css" href="' + url + '" />');
 },

 styleLoad:function(list, url){
   for(var i in list){
     document.getElementsByTagName("link")[list[i]].href = this._dir + url[i];
   }
 },

 browser:function(){
   if(navigator.appName == "Microsoft Internet Explorer"){
if(navigator.appVersion.match(/7./i)=='7.') 
{ 
     return "FF";
}else{ 
     return "IE";
} 
   }else{
     return "FF";
   }
 }
}
var test = new StyleClass("/css/");//存放CSS文件的位置
if(test.browser() == "IE"){
 test.styleWrite("ie.css");
}else{
 test.styleWrite("ff.css");
}