var pics;
pics = new Array();

function preload(name, image1, image2) {
	pics[name] = new Array(3);
	pics[name][0] = new Image();
	pics[name][0].src = image1;
	pics[name][1] = new Image();
	pics[name][1].src = image2;
}

function on(name) {
	document.images[name].src = pics[name][1].src;
}

function off(name) {
	document.images[name].src = pics[name][0].src;
}

preload('home', 'images/button-home-a.gif', 'images/button-home-b.gif');
preload('info', 'images/button-info-a.gif', 'images/button-info-b.gif');
preload('trolley', 'images/button-trolley-a.gif', 'images/button-trolley-b.gif');
preload('account', 'images/button-account-a.gif', 'images/button-account-b.gif');
preload('news', 'images/button-news-a.gif', 'images/button-news-b.gif');
preload('tandc', 'images/button-tandc-a.gif', 'images/button-tandc-b.gif');
preload('qanda', 'images/button-qanda-a.gif', 'images/button-qanda-b.gif');