if (document.images) {
    // preload the alternate images offscreen
   livewireon = new Image();
   livewireon.src = "./images/livewireb.jpg";

   infoon = new Image();
   infoon.src = "./images/infob.jpg";

   promoon = new Image();
   promoon.src = "./images/promob.jpg";

   homeworkon = new Image();
   homeworkon.src = "./images/homeworkb.jpg";

   sportson = new Image();
   sportson.src = "./images/sportsb.jpg";

   wildon = new Image();
   wildon.src = "./images/wildb.jpg"; 

   planet1on = new Image();
   planet1on.src = "./images/planet1b.jpg";

   movieon = new Image();
   movieon.src = "./images/movieb.jpg"; 

   netradiologoon = new Image();
   netradiologoon.src = "./images/netradiologob.jpg"; 


   livewireoff = new Image();
   livewireoff.src = "./images/livewire.jpg";

   infooff = new Image();
   infooff.src = "./images/info.jpg";

   promooff = new Image();
   promooff.src = "./images/promo.jpg";

   homeworkoff = new Image();
   homeworkoff.src = "./images/homework.jpg";

   sportsoff = new Image();
   sportsoff.src = "./images/sports.jpg";

   wildoff = new Image();
   wildoff.src = "./images/wild.jpg"; 

   planet1off = new Image();
   planet1off.src = "./images/planet1.jpg";

   movieoff = new Image();
   movieoff.src = "./images/movie.jpg"; 

   netradiologooff = new Image();
   netradiologooff.src = "./images/netradiologo.jpg"; 

}   
function imgOn(imgName) {
  if (document.images) {
     document[imgName].src = eval(imgName + "on.src");
 }
}
function imgOff(imgName) {
  if (document.images) {
     document[imgName].src = eval(imgName + "off.src");
 }
}