var prev = null;
 
 function menu_click(id) {
	
	if (prev != null && prev != id) {
		
		var el = document.getElementById(prev);
		el.style.display = 'none';
	}
	prev = id;
	
	var el = document.getElementById(id);
	
	
	if (el.style.display == 'none') {
		
		el.style.display = 'block';
	} else {
		
		el.style.display = 'none';
	}
	
	return false;
 }