function changeVisibility(a) {
  if (document.getElementById) {
    if (document.getElementById(a).style.visibility == "visible") {
      document.getElementById(a).style.visibility = "hidden";
    } else {
      document.getElementById(a).style.visibility = "visible";
    }
  } else if (document.all) {
    if (document.all[a].style.visibility == "visible") {
      document.all[a].style.visibility = "hidden";
    } else {
      document.all[a].style.visibility = "visible";
    }
  } else if (document.layers) {
    if (document.layers[a].style.visibility == "show") {
      document.layers[a].style.visibility = "hidden";
    } else {
      document.layers[a].style.visibility = "show";
    }
  }
}

function popup(mylink,windowname) {
  if (!window.focus) return true;
  var href;
  if (typeof(mylink) == 'string') 
     href=mylink;
  else
     href=mylink.href;
  window.open(href,windowname,'width=555,height=222,scrollbars=no');
  return false;
}