if (document.images) {

  image1on = new Image();
  image1on.src = "images/nav/1_on.jpg";
  
  image2on = new Image();
  image2on.src = "images/nav/2_on.jpg";

  image3on = new Image();
  image3on.src = "images/nav/3_on.jpg";

  image4on = new Image();
  image4on.src = "images/nav/4_on.jpg";

  image5on = new Image();
  image5on.src = "images/nav/5_on.jpg";

  image6on = new Image();
  image6on.src = "images/nav/6_on.jpg";

  image7on = new Image();
  image7on.src = "images/nav/1_6_on.jpg";

  image8on = new Image();
  image8on.src = "images/nav/v-map-on.gif";

  image9on = new Image();
  image9on.src = "images/nav/gallery-on.gif";

  image10on = new Image();
  image10on.src = "images/nav/contact-on.gif";

  image11on = new Image();
  image11on.src = "images/nav/home-on.gif";

  image1off = new Image();
  image1off.src = "images/nav/1_off.jpg";
  
  image2off = new Image();
  image2off.src = "images/nav/2_off.jpg";
  
  image3off = new Image();
  image3off.src = "images/nav/3_off.jpg";
  
  image4off = new Image();
  image4off.src = "images/nav/4_off.jpg";
  
  image5off = new Image();
  image5off.src = "images/nav/5_off.jpg";
  
  image6off = new Image();
  image6off.src = "images/nav/6_off.jpg";
  
  image7off = new Image();
  image7off.src = "images/nav/1_6_off.jpg";
  
  image8off = new Image();
  image8off.src = "images/nav/v-map.gif";
  
  image9off = new Image();
  image9off.src = "images/nav/gallery.gif";
  
  image10off = new Image();
  image10off.src = "images/nav/contact.gif";
  
  image11off = new Image();
  image11off.src = "images/nav/home.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");
  }
}