protected void Application_Error(object sender, EventArgs e)

            {           

                Exception ex = Server.GetLastError();

                if (ex is HttpException)

                {

                    if (((HttpException)(ex)).GetHttpCode() == 404)

                        Server.Transfer("~/404.html");

                }

                // Code that runs when an unhandled error occurs

                Server.Transfer("~/GenericError.htm");

    

            }