function showCards()    {
  if (navigator.appName == "Netscape")  {
          document.id4.visibility = "visible"
          document.id5.visibility = "visible"}
  else {
          document.all.id4.style.visibility = "visible"
          document.all.id5.style.visibility = "visible"}
}

function showSolution() {
  if (navigator.appName == "Netscape")  {
          document.id6.visibility = "visible" }
  else {
          document.all.id6.style.visibility = "visible"}
}

function hideAll()    {
  if (navigator.appName == "Netscape")  {
          document.id4.visibility = "hidden"
          document.id5.visibility = "hidden"
          document.id6.visibility = "hidden"}
  else {
          document.all.id4.style.visibility = "hidden"
          document.all.id5.style.visibility = "hidden"
          document.all.id6.style.visibility = "hidden"}
}