function show(id) {
  var names = document.getElementById('menu').getElementsByTagName('img');
  for (i = 1; i < names.length; i++) names[i].style.display = 'none';
  document.getElementById(id).style.display = 'block';
}

function hide(id) {
  var names = document.getElementById('menu').getElementsByTagName('img');
  for (i = 1; i < names.length; i++) {
	  if (names[i].alt == '-') names[i].style.display = 'block';
		else names[i].style.display = 'none';
	}
}