app/views/layouts/_flashes.html.erb
<% set_devise_notice_to_flash %>
<% if any_accepted_flash? %>
<div class="flashes">
<% each_accepted_flash do |type, message| %>
<div class="<%= flash_htmlclass_for type %>">
<%= button_to "#", :class => "close", "data-dismiss" => "alert", :aria_label => "Close" do %>
<span aria-hidden="true">×</span>
<% end %>
<%= message.to_s %>
</div>
<% end %>
</div>
<% end %>