var globalSelectedMenu = "";

function toggleMenu(id)
{    
    var selectedMenu = document.getElementById('menu'+globalSelectedMenu);
        
    if (selectedMenu != null && typeof selectedMenu != "undefined") 
        selectedMenu.className = "invis"; 
          
    var menu = document.getElementById('menu'+id);
    
    if (menu != null && typeof menu != "undefined")
    {
        if (menu.className == "invis" && globalSelectedMenu != id)
        {
            menu.className = "vis";
            globalSelectedMenu = id;
        }
        else
        {
            menu.className = "invis";
            globalSelectedMenu = "";
        }       
    }
}