var onArray = new Array ("homeon.gif",
			"factson.gif",
			"mapon.gif",
			"quizon.gif",
			"gameon.gif",
			"productson.gif");

var offArray = new Array ("homeoff.gif",
			"factsoff.gif",
			"mapoff.gif",
			"quizoff.gif",
			"gameoff.gif",
			"productsoff.gif");

function setButtonOn(index) {
  document.images[index].src = "images/" + onArray[index];
}

function setButtonOff(index) {
  document.images[index].src = "images/" + offArray[index];
}