add_to_collection_success.html.erb

<div data-ajax-modal="container">
  <div class="modal-header">
    <button type="button" class="ajax-modal-close close close-reveal-modal" data-dismiss="modal" aria-hidden="true">×</button>
    <h1 class="modal-title">Item Added</h1>
  </div>
  <div class="modal-body">
    <%= render :partial=>'/flash_msg' %>
    <span class="ajax-close-modal"></span>
  </div>
</div>