var menuActive = '';

function PropertiesRef(id) {
  var r;
	if (document.layers) return document.layers[id];
	if (document.all && (r = document.all[id])) return r.style;
	if (r = document.getElementById(id)) return r.style;
	else return null;
};

function LayerShow(id) {
	var r; if (r = PropertiesRef(id)) r.visibility = 'visible';
}

function LayerHide(id) {
  var r; if (r = PropertiesRef(id)) r.visibility = 'hidden';
}

function MenuShow(id) {
	if (menuActive) MenuHide(menuActive);
	LayerShow(id);
	var parts = id.split('/');
	while (parts.length > 2) {
		parts.pop();
		LayerShow(parts.join('/') + '/');
	}
	menuActive = id;
}

function MenuHide(id) {
	LayerHide(id);
	var parts = id.split('/');
	while (parts.length > 2) {
		parts.pop();
		LayerHide(parts.join('/') + '/');
	}
	menuActive = '';
}