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) {
		nav_button_1_over_28 = newImage("nav/nav_button-1_over_28.jpg");
		nav_button_2_over_29 = newImage("nav/nav_button-2_over_29.jpg");
		nav_button_3_over_30 = newImage("nav/nav_button-3_over_30.jpg");
		nav_button_4_over_31 = newImage("nav/nav_button-4_over_31.jpg");
		nav_button_5_over_32 = newImage("nav/nav_button-5_over_32.jpg");
		nav_button_6_over_33 = newImage("nav/nav_button-6_over_33.jpg");
		preloadFlag = true;
	}
}