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_flugzeuge_over = newImage("/img/nav_flugzeuge-over.gif");
			    nav_thermo_over = newImage("/img/nav_thermo-over.gif");
			    nav_visionen_over = newImage("/img/nav_visionen-over.gif");
			    nav_leben_over = newImage("/img/nav_leben-over.gif");
			    nav_motoren_over = newImage("/img/nav_motoren-over.gif");
			    nav_reklame_over = newImage("/img/nav_reklame-over.gif");
			    preloadFlag = true;
			  }
			}