opened = null;

function toggleSub(id) {

	if((opened != null ) && (opened != id))
		document.getElementById('sub-' + opened).style.display = 'none';
	
	s = document.getElementById('sub-' + id);

	if(s.style.display == 'block') {
		s.style.display = 'none';
		opened = null;
	} else {
		s.style.display = 'block';
		opened = id;
	}
}