lib/responders_backport/responder.rb
def navigation_behavior(error)
      if get?
        raise error
      elsif has_errors? && default_action
        render :action => default_action
      else
        redirect_to resource_location
      end
    end
def navigation_behavior(error)
      if get?
        raise error
      elsif has_errors? && default_action
        render :action => default_action
      else
        redirect_to resource_location
      end
    end
This is the common behavior for "navigation" requests, like :html, :iphone and so forth.