function open_win(u, w, h) { 
            var l = (screen.width - w) / 2; 
            var t = (screen.height - h) / 2; 
            var s = 'width=' + w + ', height=' + h + ', top=' + t + ', left=' + l; 
            s += ', toolbar=no, scrollbars=no, menubar=no, location=no, resizable=no'; 
            open(u, 'oWin', s); 
      }