function SwitchMenu(obj){
        if(document.getElementById){
        var el = document.getElementById(obj);
        var ar = document.getElementById("menuprinc").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";
        }
        }
    }