function changeImage(img, newSrc) {
	img.setAttribute("src", newSrc);
}

ele=new Image();
ele.src="images/button-elevators-over.gif";

sta=new Image();
sta.src="images/button-stair-lifts-over.gif";

dum=new Image();
dum.src="images/button-dumbwaiters-over.gif";

mor=new Image();
mor.src="images/button-more-products-over.gif";