if (document.images) {
  image1on = new Image();
  image1on.src = "images/nav_homeon.gif";
  image2on = new Image();
  image2on.src = "images/nav_teamon.gif";
  image3on = new Image();
  image3on.src = "images/nav_listenon.gif";
  image4on = new Image();
  image4on.src = "images/nav_orderon.gif";
  image5on = new Image();
  image5on.src = "images/nav_contacton.gif";


  image1off = new Image();
  image1off.src = "images/nav_home.gif";
  image2off = new Image();
  image2off.src = "images/nav_team.gif";
  image3off = new Image();
  image3off.src = "images/nav_listen.gif";
  image4off = new Image();
  image4off.src = "images/nav_order.gif";
  image5off = new Image();
  image5off.src = "images/nav_contact.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");
  }
}