function popup(url, width, height) {
  //alert(window.screen.width + ", " + window.screen.height);
  var top = (window.screen.height - height) / 2;
  var left = (window.screen.width - width) / 2;
  window.open(url, '_blank', 'width=' + width + ',height=' + height + ',top=' + top + ',left=' + left + ',fullscreen=yes,scrollbars=no,centerscreen=yes');
}