var preloaded = false;

function getImg(addr) {
	if (document.images) {
		ary = new Image();
		ary.src = addr;
		return ary;
	}
}

function swap(bname, bsrc) {
	if (preloaded == true) {
		document[bname].src = bsrc;
	}
}

function doPreload() {
	if (document.images) {
		order_up = getImg("images/orderBooks-on.gif");
		details_up = getImg("images/bookDetails-on.gif");
		about_up = getImg("images/aboutUs-on.gif");
		contact_up = getImg("images/contactUs-on.gif");
		whatis_up = getImg("images/whatIs-on.gif");
		preloaded = true;
	}
}