if($("txtUsername"))
{
  $("txtUsername").value = "Uživatelské jméno";

  $("txtUsername").observe("focus", function()
  {
    if(this.value == "Uživatelské jméno")
    {
      this.value = "";
    }
  });

  $("txtUsername").observe("blur", function()
  {
    if(this.value == "")
    {
      this.value = "Uživatelské jméno";
    }
  });
}

if($("txtPassword"))
{
  $("txtPassword").type = "text";
  $("txtPassword").value = "Heslo";

  $("txtPassword").observe("focus", function()
  {
    if(this.value == "Heslo")
    {
      try
      {
        this.type = "password";
      }
      catch(err)
      {
        //nothing to do here
      }

      this.value = "";
    }
  });

  $("txtPassword").observe("blur", function()
  {
    if(this.value == "")
    {
      try
      {
        this.type = "text";
      }
      catch(err)
      {
        //nothing to do
      }

      this.value = "Heslo";
    }
  });
}