var ready = false;
if (document.images){
 if (((navigator.appCodeName == 'MSIE') && (navigator.appVersion.substring(0,1) > 3)) ||
 ((navigator.appCodeName == 'Mozilla') && (navigator.appVersion.substring(0,1) > 2))) { ready = true; }
 if (ready){
  var ready = true
  enter_on = new Image()
  enter_off = new Image()
  enter_on.src="images/enter_on.gif"
  enter_off.src="images/enter_off.gif"
  function activate(img) {
   if (ready){document[img].src = eval (img + "_on.src");}
  }
  function deactivate(image) {
   if (ready){document[image].src = eval (image + "_off.src");}
  }
 }
}