function Kontrola ()
{
   if (document.order.jmeno.value == "")
   {
      document.order.jmeno.focus();
      alert ("Fill in your name.");
      return false;
   }
   if (document.order.prijmeni.value == "")
   {
      document.order.prijmeni.focus();
      alert ("Fill in your surname.");
      return false;
   }
   if (document.order.email.value == "")
   {
      document.order.email.focus();
      alert ("Fill in your e-mail");
      return false;
   }
   if (document.order.email.value.indexOf("@") == -1)
   {
      document.order.email.focus();
      alert ("Invalid format of e-mailu");
      return false;
   }
}