var id_menu = new Array('sub_menu_1','sub_menu_2','sub_menu_3','sub_menu_4');
function allclose() { for (i=0; i < id_menu.length; i++){  
document.getElementById(id_menu[i]).style.display = "none"; 
}
}
function openMenu(id){ 
for (i=0; i < id_menu.length; i++){  
if (id != id_menu[i]){   
document.getElementById(id_menu[i]).style.display = "none";  
} 
} 
document.getElementById(id).style.display = "block"; 

}