form_verzonden = 0;
function test(velden) {
  if (velden.email.value.indexOf("@")  == -1  ||
      velden.email.value.indexOf(".")  == -1  ||
      velden.email.value.length         <  6  ||
      velden.email.value.indexOf(" ")   >  0  ||
      velden.email.value.indexOf(",")   >  0  ||
      velden.email.value.indexOf("'")   >  0  ||
      velden.email.value.indexOf("/")   >  0  ||
      velden.email.value.indexOf("\\")  >  0  ||
      velden.email.value.indexOf("<") != -1 ||
      velden.email.value.indexOf(">") != -1 ||
      velden.email.value.indexOf("@") > velden.email.value.lastIndexOf(".")
     ) {
    e_mail_ok = 0;
  } else {
    e_mail_ok = 1;
  }

  if (e_mail_ok == 0 && velden.email.value.length > 0 )
  { alert("Uw e-mailadres is onjuist.");
    velden.email.focus();
  } else

  if (velden.email.value.length < 4 )
  { alert("Uw emailadres ontbreekt.");
    velden.email.focus();
  } else

  if (velden.naam.value.length < 2 )
  { alert("Uw naam ontbreekt.");
    velden.naam.focus();
  } else

  if (velden.telefoon.value.length < 5 )
  { alert("Uw telefoonnummer ontbreekt.");
    velden.telefoon.focus();
  } else

  if (velden.mededelingen.value.length < 5 )
  { alert("Uw mededeling ontbreekt.");
    velden.mededelingen.focus();
  } else

  {
    if (form_verzonden == 0) {
      form_verzonden = 1;
      return (true);
    }
  }
  return (false);
}