Bootstrap3: centered modal with close button

gistfile1.txt

  <!-- modal Dialog -->
  <!--.modal.fade#sentDialog>.modal-dialog>.modal-content-->
  <div id="sentDialog" class="modal fade " tabindex="-1">
    <div class="modal-dialog " id="modal-centered-absolute">
      <div class="modal-content">
        <div class="modal-header">
          <a href="#" class="close" data-dismiss="modal">&times;</a>
          <h4>Thanks for clicking!</h4>

        </div>
        <div class="modal-body">
          <p>Are you Sure?</p>
        </div>
        <div class="modal-footer">
          <button class="btn btn-success" data-dismiss="modal">Close</button>
        </div>
      </div>
    </div>
  </div>