function popup(theURL,w,h) {
  wleft = (screen.width - w) / 2;
  wtop = (screen.height - h) / 2;

  if (wleft < 0) {
    w = screen.width;
    wleft = 0;
  }
  if (wtop < 0) {
    h = screen.height;
    wtop = 0;
  }	

 t="toolbar=no,left="+ wleft +",top="+ wtop +",location=no,directories=no,status=no,menubar=no,scrollbars=yes,resizable=yes,copyhistory=no,width="+w+",height="+h+")";
 window.open(theURL,'lalala',t);
}