function domenu(sub)
{
  if (document.getElementById) {
    document.getElementById('subm_1').style.visibility = "hidden";
    document.getElementById('subm_2').style.visibility = "hidden";
    document.getElementById('subm_3').style.visibility = "hidden";
    if (sub > 0) { document.getElementById('subm_'+sub).style.visibility = "visible"; }
  } else if (document.layers) {
    document.subm_1.visibility = "hide"; 
    document.subm_2.visibility = "hide";
    document.subm_3.visibility = "hide";
    if (sub > 0) { document['subm_'+sub].visibility = "show"; }
  } else if (document.all) {
    document.all.subm_1.style.visibility = "hidden"; 
    document.all.subm_2.style.visibility = "hidden";
    document.all.subm_3.style.visibility = "hidden";
    if (sub > 0) { document.all['subm_'+sub].style.visibility = "visible"; }
  }
}