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) {
		home_over = newImage("images/home-over.png");
		home_up = newImage("images/home-on.png");
		kids_over = newImage("images/kids-over.png");
		kids_up = newImage("images/kids-on.png");
		parents_over = newImage("images/parents-over.png");
		parents_up = newImage("images/parents-on.png");
		teachers_over = newImage("images/teachers-over.png");
		teachers_up = newImage("images/teachers-on.png");
		download_over = newImage("images/download-yellow.png");
		blueback_over = newImage("images/back-blue-yellow.png");
		yellowback_over = newImage("images/back-yellow-yellow.png");


		preloadFlag = true;
	}
}