if (document.images) {
   homeOn = new Image();
   homeOn.src = "images/home-on.gif";
   homeOff = new Image();
   homeOff.src = "images/home-off.gif";
   }

if (document.images) {
   aboutOn = new Image();
   aboutOn.src = "images/about-on.gif";
   aboutOff = new Image();
   aboutOff.src = "images/about-off.gif";
   }

if (document.images) {
   studioOn = new Image();
   studioOn.src = "images/studio-on.gif";
   studioOff = new Image();
   studioOff.src = "images/studio-off.gif";
   }

if (document.images) {
   contactOn = new Image();
   contactOn.src = "images/contact-on.gif";
   contactOff = new Image();
   contactOff.src = "images/contact-off.gif";
   }

function activate(image_name) {
   if (document.images) {
       document[image_name].src = eval(image_name + "On.src");
   }
   }

function deactivate(image_name) {
   if (document.images) {
       document[image_name].src = eval(image_name + "Off.src");
   }
}