function navInit() {
	// preload images
	var versionSuffix = '_home';
	for (var i=1; i<topNavItems.length; i++) {
		var imgID = i;
		topNavOff[i] = new Image();
		topNavOff[i].src = 'img/primary_nav' + versionSuffix + '_' + imgID + '_off.gif';
		topNavOver[i] = new Image();
		topNavOver[i].src = 'img/primary_nav' + versionSuffix + '_' + imgID + '_over.gif';
	}
}
navInit();