function preloadImages() {
	if (document.images) {
		pre_intern_a = newImage('../images/buttons/intern_a.jpg');
		pre_extern_a = newImage('../images/buttons/extern_a.jpg');
		pre_lohn_a = newImage('../images/buttons/lohn_a.jpg');
		pre_zurueck_a = newImage('../../images/buttons/zurueckg_a.jpg');
		preloadFlag = true;
	}
}