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

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

  image3on = new Image();
  image3on.src = "images/navigation_on_location.gif";
  
  image4on = new Image();
  image4on.src = "images/navigation_on_contact.gif";

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

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

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

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

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

  image5off = new Image();
  image5off.src = "images/navigation_off_autoparts.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");
  }
}