preloadFlag=1;
nb='_over';

function on(button) {
		if(preloadFlag==1 & button.src.indexOf('_active')<=0){
		x = button.src;
		y = x.substring(0,x.length-4);
		ext = x.substring(x.length-4,x.length);
		act=y+nb+ext;
		button.src=act;
		 }
}

function off(button) {
		x = button.src;
		ext = x.substring(x.length-4,x.length);
		tocut = x.length-(nb.length+ext.length);
		if (x.indexOf(nb)>0) {
		  y = x.substring(0,tocut);
		  act = y+ext;
		  button.src=act;
		 }
}