if (document.images) {
    // preload the alternate images offscreen
   friendson = new Image();
   friendson.src = "./images/friends1on.gif";
   familyon = new Image();
   familyon.src = "./images/family1on.gif";
   radioson = new Image();
   radioson.src = "./images/radios1on.gif";
   
   friendsoff = new Image();
   friendsoff.src = "./images/friends1off.gif";
   familyoff = new Image();
   familyoff.src = "./images/family1off.gif";
   radiosoff = new Image();
   radiosoff.src = "./images/radios1off.gif";
}   
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");
 }
}