function na_blink(speed) 
{
  if (speed) {
    if (document.all)
      setInterval("na_blink()", speed*100)
    return;
  }
  var blink = document.all.tags("blink") 
  for (var i=0; i<blink.length; i++)
    blink[i].style.visibility = blink[i].style.visibility == "" ? "hidden" : "" 
}