if (document.images) {
  image1on = new Image();
  image1on.src = "images/artforsale_on.gif";

  image1off = new Image();
  image1off.src = "images/artforsale_off.gif";

  image2on = new Image();
  image2on.src = "images/portfolio_on.gif";

  image2off = new Image();
  image2off.src = "images/portfolio_off.gif";

  image3on = new Image();
  image3on.src = "images/comicart_on.gif";

  image3off = new Image();
  image3off.src = "images/comicart_off.gif";

  image4on = new Image();
  image4on.src = "images/bio_on.gif";

  image4off = new Image();
  image4off.src = "images/bio_off.gif";

  image5on = new Image();
  image5on.src = "images/textop_on.gif";

  image5off = new Image();
  image5off.src = "images/textop_off.gif";

  image6on = new Image();
  image6on.src = "images/store_on.gif";

  image6off = new Image();
  image6off.src = "images/store_off.gif";
}

function turnOn(imageName) {
  if (document.images) {
    document[imageName].src =
      eval(imageName + 'on.src');
  }
}

function turnOff(imageName) {
  if (document.images) {
    document[imageName].src =
      eval(imageName + 'off.src');
  }
}