var menuLast = "";

function menuVisible(id) {
  if(menuLast!="") { menuHide(menuLast); }

  if(document.getElementById(id)) {
    document.getElementById(id).style.visibility = "visible";
    menuLast = id;
  }
}
function menuHide(id) {
  if(document.getElementById(id)) {
    document.getElementById(id).style.visibility = "hidden";
  }
}