function switchmenu(obj){
    if(document.getElementById){
    var el = document.getElementById(obj);
    var ar = document.getElementById("menudiv").getElementsByTagName("span"); 
            if(el.style.display != "block"){
                    for (var i=0; i<ar.length; i++){
                            if (ar[i].className=="submenu") 
                            ar[i].style.display = "none";
                    }
                    el.style.display = "block";
            }else{
                    el.style.display = "none";
            }
    }
}