var aPreloads = new Array('nav_home', 'nav_about', 'nav_membership', 'nav_members_only', 'nav_media', 'nav_board_members', 'nav_volunteer', 'nav_speakers_bureau', 'nav_calendar', 'nav_events', 'nav_contact_us');

var sBasePath = '/images/';
var loaded = false;
function init() {
	preloadImages();
	attachMouseovers();
	loaded = true;
}

function preloadImages() {
	var over, out;
	for(var i=0; i<aPreloads.length; i++) {
		out = new Image();
		out.src = sBasePath + aPreloads[i] + '.gif';
		window[aPreloads[i]] = out;

		over = new Image();
		over.src = sBasePath + aPreloads[i] + '_on.gif';
		window[aPreloads[i] + '_on'] = over;
	}
}

function attachMouseovers() {
	var aImgs = document.getElementById('nav').getElementsByTagName('img');
	for(var i=0; i<aImgs.length; i++) {
		if(aImgs[i].src.indexOf('_on.gif') == -1) {
			aImgs[i].onmouseover = swapImage;
			aImgs[i].onmouseout= swapImage;
		}
	}
}

function swapImage() {
	if(!loaded) return false;
	var sImg = this.id;
	if(this.src.indexOf('_on.gif') == -1) {
		this.src = eval(sImg + '_on.src');
	} else {
		this.src = eval(sImg + '.src');
	}
}

window.onload = init;