function menuShow(id) {

  var element = document.getElementById(id);
  if (element) { element.className = 'menuitem visible'; }
  element = document.getElementById('content');
  if (element) { element.className = 'menudown'; }

}

function menuHide(id) {

  var element = document.getElementById(id);
  if (element) { element.className = 'menuitem'; }
  element = document.getElementById('content');
  if (element) { element.className = ''; }

}