function show_hide(id) {
  if (! document.getElementById) return;
  if (document.getElementById(id).style.display != "block")
    document.getElementById(id).style.display = "block";
  else
    document.getElementById(id).style.display = "none";
}

function hide_show(id) {
  if (! document.getElementById) return;
  if (document.getElementById(id).style.display != "none")
    document.getElementById(id).style.display = "none";
  else
    document.getElementById(id).style.display = "block";
}