function newImage(arg) {
	if (document.images) {
		rslt = new Image();
		rslt.src = arg;
		return rslt;
	}
}

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

var preloadFlag = false;
function preloadImages() {
	if (document.images) {
		btn_yellow_over = newImage("images/btn-yellow-over.gif");
		btn_orange_over = newImage("images/btn-orange-over.gif");
		btn_blue_over = newImage("images/btn-blue-over.gif");
		btn_green_over = newImage("images/btn-green-over.gif");
		btn_purple_over = newImage("images/btn-purple-over.gif");
		btn_red_over = newImage("images/btn-red-over.gif");
		preloadFlag = true;
	}
}