function show_hide_error_type() {
  show_hide_field_on_dropdown_condition('contact_form', 'question_type', Array('errors'), 'ad_related_error_field');
  toggle_ad_number_class();
}

function toggle_ad_number_class() {
  var form = document.forms['contact_form'];
  var ad_related_error_dropdown = form.elements['ad_related_error'];
  var is_ad_related_error = ad_related_error_dropdown.options[ad_related_error_dropdown.selectedIndex].value;
  var question_type_dropdown = form.elements['question_type'];
  var question_type = question_type_dropdown.options[question_type_dropdown.selectedIndex].value;

  var ad_number_required = document.getElementById('ad_number_required');
  if ( is_ad_related_error == 'yes' && question_type == 'errors' ) {
    ad_number_required.className = 'fieldRequired';
    ad_number_required.innerHtml = '(Required)';
  }
  else {
    ad_number_required.className = '';
    ad_number_required.innerHtml = '';
  }
}