window.onload = rolloverInit;

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

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

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

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

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