function popup (url, name, width, height, resizable) {
  var posX = screen.width  / 2 - width  / 2;
  var posY = screen.height / 2 - height / 2;
  obj = window.open (url, name, 'status=no,toolbar=no,menubar=no,location=no,scrollbars=yes, width=' + width + ', height=' + height + ', left=' + posX + ', top=' + posY + (resizable ? ', resizable=yes' : ''));
  return false;
}