// check validity and precence of data regard newsletter signup form
function checkNewsletterForm() {
  toCheckForm = document.getElementById('newsletterForm');
  var error = '';
  
  var name = trim(toCheckForm.name.value);
  var surname = trim(toCheckForm.surname.value);
  var email = trim(toCheckForm.email.value);
  var privacy = toCheckForm.privacy.checked
  var company = trim(toCheckForm.company.value);


  // check name
  if (name == '')
    error += _INFOFORMERROR1_ + '!\n';
  else if (name.length > 50)
    error += _INFOFORMERROR2_ + '!\n';
  
  // check surname
  if (surname == '')
    error += _INFOFORMERROR3_ + '!\n';
  else if (surname.length > 70)
    error += _INFOFORMERROR4_ + '!\n';
  
  // check email
  if (email == '')
    error += _INFOFORMERROR5_ + '!\n';
  else if (email.length > 100)
    error += _INFOFORMERROR6_ + '!\n';
  else if (!checkEmail(email))
    error += _INFOFORMERROR7_ + '!\n';
  
  // check privacy agreement
  if (!privacy)
    error += _INFOFORMERROR12_ + '!\n';
  
  // check company
  if (company.length > 100)
    error += _INFOFORMERROR9_ + '!\n';

  if (error != "") {
    window.alert (_WARNING_ + ':\n' + error + '\n' + _WARNINGADVICE_ + '.');
    return false;
  }
  return true;
} // end of checkInfoRequestForm