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) {
		background_over = newImage("images/background-over.gif");
		topography_over = newImage("images/topography-over.gif");
		beforemadikwe_over = newImage("images/beforemadikwe-over.gif");
		wildlife_over = newImage("images/wildlife-over.gif");
		animalspecies_over = newImage("images/animalspecies-over.gif");
		birdspecies_over = newImage("images/birdspecies-over.gif");
		treespecies_over = newImage("images/treespecies-over.gif");
		reptilespecies_over = newImage("images/reptilespecies-over.gif");
		grasspecies_over = newImage("images/grassspecies-over.gif");
		frogspecies_over = newImage("images/frogspecies-over.gif");
		preloadFlag = true;
	}
}