function provjera(form_upitnik){

  if (form_upitnik.ime.value == "")
  {
    alert("Morate upisati Vaše ime!");
    form_upitnik.ime.focus();
    return (false);
  }

  if (form_upitnik.e_mail.value == "")
  {
    alert("Morate upisati Vaš E-Mail!");
    form_upitnik.e_mail.focus();
    return (false);
  }
}