function blink() {
  if (!document.all) { return; }
  for (i = 0; i < document.all.length; i++) {
    obj = document.all(i);
    if (obj.className == "blink") {
      if (obj.style.visibility == "visible") {
        obj.style.visibility = "hidden";
      } 
      else {
        obj.style.visibility = "visible";
      }
    }
  }
  setTimeout("blink()", 600);
}