app/views/shared/_error_messages.html.erb
<% if object.errors.any? %>
<div id="error explanation">
<div id="alert alert-error">
The form contains <%= pluralize(object.errors.count, "error")%>.
</div>
<ul>
<% object.errors.full_messages.each do |msg| %>
<li>* <%= msg %></li>
<% end %>
</ul>
</div>
<% end %>