function popImages(w, h) {
  posy = (screen.height - h)/2;
  posx = (screen.width - w)/2;
  param = new String("width=" + w + ",height=" + h + ",screenX=" + posx + ",screenY=" + posy + ",resizable=yes,dependent=yes,scrollbars=no, status=no");
  popup = window.open("", "galerie", param);
  popup.focus();
}