function twvalidate() {
  if (isEmpty(document.twdownload.firstname.value)) {
      alert('Please enter your first name.');
      return false;
  }

  if (isEmpty(document.twdownload.lastname.value)) {
      alert('Please enter your last name..');
      return false;
  }

  if (isEmpty(document.twdownload.email.value) || (!isEmail(document.twdownload.email.value))) {
      alert('Please enter your email address.');
      return false;
  }

  if (isEmpty(document.twdownload.zip.value) || (!isZIPCode(document.twdownload.zip.value))) {
      alert('Please enter your zip.');
      return false;
  }

  if (document.twdownload.Wildcard1.value == 'choose') {
      alert('Please tell us if you are a member of SNCR.');
      return false;
  }

  document.twdownload.referral_id.value = QString('referral_id');
  if (document.twdownload.referral_id.value == 'undefined')
      document.twdownload.referral_id.value = '';

  return true;
}