if (document.images) {

  imageAon = new Image();
  imageAon.src = "../img/navbot_1on.gif";
  imageBon = new Image();
  imageBon.src = "../img/navbot_2on.gif";
  imageCon = new Image();
  imageCon.src = "../img/navbot_3on.gif";
  imageDon = new Image();
  imageDon.src = "../img/navbot_4on.gif";

  imageAoff = new Image();
  imageAoff.src = "../img_fed/navbot_1off.gif";
  imageBoff = new Image();
  imageBoff.src = "../img_fed/navbot_2off.gif";
  imageCoff = new Image();
  imageCoff.src = "../img_fed/navbot_3off.gif";
  imageDoff = new Image();
  imageDoff.src = "../img_fed/navbot_4off.gif";

}

function changeImages() {
  if (document.images) {
    for (var i=0; i<changeImages.arguments.length; i+=2) {
      document[changeImages.arguments[i]].src = eval(changeImages.arguments[i+1] + ".src");
    }
  }
}