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) {
		btn_boilers_over = newImage("images/btn_boilers-over.gif");
		btn_boilers_down = newImage("images/btn_boilers-down.gif");
		btn_installations_over = newImage("images/btn_installations-over.gif");
		btn_installations_down = newImage("images/btn_installations-down.gif");
		btn_renewables_over = newImage("images/btn_renewables-over.gif");
		btn_renewables_down = newImage("images/btn_renewables-down.gif");
		btn_powerflushing_over = newImage("images/btn_powerflushing-over.gif");
		btn_powerflushing_down = newImage("images/btn_powerflushing-down.gif");
		btn_unvented_over = newImage("images/btn_unvented-over.gif");
		btn_unvented_down = newImage("images/btn_unvented-down.gif");
		btn_underfloor_over = newImage("images/btn_underfloor-over.gif");
		btn_underfloor_down = newImage("images/btn_underfloor-down.gif");
		btn_home_over = newImage("images/btn_home-over.gif");
		btn_home_down = newImage("images/btn_home-down.gif");
		btn_gallery_over = newImage("images/btn_gallery-over.gif");
		btn_gallery_down = newImage("images/btn_gallery-down.gif");
		btn_contact_over = newImage("images/btn_contact-over.gif");
		btn_contact_down = newImage("images/btn_contact-down.gif");
		btn_links_over = newImage("images/btn_links-over.gif");
		btn_links_down = newImage("images/btn_links-down.gif");
		preloadFlag = true;
	}
}