function toggle(submenu) { 
	if (document.getElementById(submenu).style.display == "none") 
		document.getElementById(submenu).style.display = "block"; 
	else if (document.getElementById(submenu).style.display == "block") 
		document.getElementById(submenu).style.display = "none" 
	else 
		alert("An error occured in the menu."); 
}