In order to validate forms added to the page dynamically the validate function needs to be called for that form.
If you dynamically render the following rails template into you view:
<%= form_for @some_model, :validate => true, :id => 'my_dynamic_form' do |f| %> <%= f.text_field :some_attribute %> <% end %>
you will need to call:
to have form validate client side.