Bootstrap3: modal Dialog tabIndex="-1" -- to prevent accidental tabbing

gistfile1.txt

  <!-- modal Dialog -->
  
  <a href="#sentDialog" class="btn btn-info" data-toggle="modal">Show Dialog</a>
  
  <!--.modal.fade#sentDialog>.modal-dialog>.modal-content-->
  <div id="sentDialog" class="modal fade" tabindex="-1">
    <div class="modal-dialog">
      <div class="modal-content">
        <div class="modal-header">Thanks for clicking!</div>
        <div class="modal-body">
          <p>Are you Sure?</p>
        </div>
        <div class="modal-footer">
          <button class="btn btn-success">Close</button>
        </div>
      </div>
    </div>
  </div>