function openDiv(id) {
	switch ( id ) {
		case "primo":
			document.getElementById('submenu_01').style.display = 'block';
			break;
	    case "secondo":
			document.getElementById('submenu_02').style.display = 'block';	
			break;
	}
}
function closeDiv(id) {
	switch ( id ) {
		case "primo":
			document.getElementById('submenu_01').style.display = 'none';	
			break;
		case "secondo":
			document.getElementById('submenu_02').style.display = 'none';	
			break;
	}
}