contactOn = new Image(40, 78);
contactOn.src = "/img/NAV-contact-on.gif";
contactOff = new Image(40, 78);
contactOff.src = "/img/NAV-contact.gif";
helpOn = new Image(32, 78);
helpOn.src = "/img/NAV-help-on.gif";
helpOff = new Image(32, 78);
helpOff.src = "/img/NAV-help.gif";
goOn = new Image(23, 21);
goOn.src = "/img/BUTTON-go-on.gif";
goOff = new Image(23, 21);
goOff.src = "/img/BUTTON-go.gif";

function imageOn(imgName) {
  imgOn = eval(imgName + "On.src");
  document[imgName].src = imgOn;
}

function imageOff(imgName) {
  imgOff = eval(imgName + "Off.src");
  document[imgName].src = imgOff;
}