if (document.images) {
  image0 = new Image;
  image1 = new Image;
  image2 = new Image;
  image3 = new Image;
  image0.src = 'graphics/nacal32a.gif';
  image1.src = 'graphics/nacal32b.gif';
  image2.src = 'graphics/nacal32c.gif';
  image3.src = 'graphics/nacal32d.gif';
} else {
  image0 = '';
  image1 = '';
  image2 = '';
  image3 = '';
  document.rollimg = '';
}