function toggleMenu(node)
{
  // Unfold the branch if it isn't visible
  if (node.nextSibling.style.display == 'none')
  {
    node.nextSibling.style.display = 'block';
  }
  // Collapse the branch if it IS visible
  else
  {
    node.nextSibling.style.display = 'none';
  }
}