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) {
		navqui_over = newImage("images/navqui-over.png");
		navref_over = newImage("images/navref-over.png");
		navcat_over = newImage("images/navcat-over.png");
		navtro_over = newImage("images/navtro-over.png");
		navesp_over = newImage("images/navesp-over.png");
		navdev_over = newImage("images/navdev-over.png");
		navcon_over = newImage("images/navcon-over.png");
		preloadFlag = true;
	}
}