..
<%= javascript_include_tag :defaults %>
..
<% form_remote_tag :url => {:controller => "session", :action => "create" }, :update => 'message' do %>
...
...

		<p>
			<%= submit_tag 'create account', :class => 'btn' %>
			<!-- button class="btn" type="submit">create account</button -->
		</p>
	</div>
<% end %>