javascript的xmlhttp实现

<script language="javascript" type="text/javascript">
function f_GetHttpStr(objID,strUrl)
        {
            try
            {
                var obj=window.document.getElementById(objID);
                obj.innerHTML="下载中~~~";
                var Location = strUrl;
                var auth = new ActiveXObject("msxml2.xmlhttp");
                var ReqStr = '<?xml version="1.0" encoding="UTF-8"?>';

                auth.open("POST", Location, false);
                auth.send(ReqStr);
                //alert(auth.status);
                if(auth.status != 200)
                {
                    obj.innerHTML="加载错误,<a href=/"javascript:;/" onclick=/"dd('"+objID+"','"+strUrl+"')/">刷新</a>!!";
                }
                var responsetext = auth.ResponseText;
                obj.innerHTML=responsetext;
            }
            catch(e)
            {
                obj.innerHTML="加载错误,<a href=/"javascript:;/" onclick=/"dd('"+objID+"','"+strUrl+"')/">刷新</a>!";
            } 
        } 
</script>