function hide(what)
{
    if (!document.getElementById) {
      return null;
    }
    showWhat = document.getElementById(what);
    showWhat.style.display = "none";
  } 
  
  function show(what)
  {
    if (!document.getElementById) {
      return null;
    }
    showWhat = document.getElementById(what);
    showWhat.style.display = "block";
  }