function collapse(id) {

	if (menu == id) {
	
		cls = document.getElementById('link-' + menu).className;
		if (cls == 'active') {
			document.getElementById('link-' + menu).className = '';
			document.getElementById('menu-' + menu).style.display = 'none';	
		} else {
			document.getElementById('link-' + menu).className = 'active';
			document.getElementById('menu-' + menu).style.display = 'block';	
		}
		
	} else {	

		if (menu !== null) {
			document.getElementById('link-' + menu).className = '';
			document.getElementById('menu-' + menu).style.display = 'none';	
		}
		
		document.getElementById('link-' + id).className = 'active';
		document.getElementById('menu-' + id).style.display = 'block';	
	
	}

	menu = id;
		
}