prev = null;

function exp(id) {
	menu = document.getElementById(id);
	if (menu) {
		if (menu.className == '' || menu.className == 'closed') {
			if (prev != null) {
				prev.className = "closed";
			}
			menu.className = "opened";
			menu.className = "opened";
			prev = menu;
			return false;
		} else {
			menu.className = "closed";
			return false;
		}
	}
	return false;	
}