xmlhttprequest 请求

request.open("GET", url, false);
    request.onreadystatechange = ErrPage;
-------------------------------------
位置反过来
function ErrPage()
       {
            if (request.readyState == 4)
              {
             if (request.status == 200)
            //alert("Request URL does not exist");
              alert("success");         }
       }