function formcheck() {

if (document.kontaktform.Name.value == "" && document.kontaktform.Strasse.value == "" && document.kontaktform.PLZ.value == "" && document.kontaktform.Ort.value == "")
  {alert("Please fill out the marked fields. Thankyou");
  document.kontaktform.Name.focus();
  return false;
  }
}