window.onload = rolloverInit;

function rolloverInit() {
  for (var i=0; i<document.images.length; i++) {
  if (document.images[i].parentNode.tagName == "A") {
  setupRollover(document.images[i]);
}}}

function setupRollover(thisImage) {
  thisImage.outImage = new Image();
  thisImage.outImage.src = thisImage.src;
  thisImage.onmouseout = rollOut;

  thisImage.clickImage = new Image();
  thisImage.clickImage.src = "images/" + thisImage.id + "on.png";
  thisImage.onclick = rollClick;

  thisImage.overImage = new Image();
  thisImage.overImage.src = "images/" + thisImage.id + "on.png";
  thisImage.onmouseover = rollOver;
}

function rollOver() {
  this.src = this.overImage.src;}

function rollOut() {
  this.src = this.outImage.src;}

function rollClick() {
  this.src = this.clickImage.src;}