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) {
		top_over = newImage("oasis_menu_images/top-over.gif");
		sys_over = newImage("oasis_menu_images/sys-over.gif");
		comp_over = newImage("oasis_menu_images/comp-over.gif");
		gra_over = newImage("oasis_menu_images/gra-over.gif");
		sche_over = newImage("oasis_menu_images/sche-over.gif");
		mem_over = newImage("oasis_menu_images/mem-over.gif");
		rec_over = newImage("oasis_menu_images/rec-over.gif");
		preloadFlag = true;
	}
}