i found the solution, check this out => http://techoctave.com/c7/posts/36-rails-3-0-rescue-from-routing-error-solution (great solution)
routes.rb :
# at the end of you routes.rb
match '*a', :to => 'errors#routing', via: :get
errors_controller.rb :
class ErrorsController < ApplicationController
def routing
render_404
end
end
application.rb :
rescue_from ActionController::RoutingError, :with => :render_404
private
def render_404(exception = nil)
if exception
logger.info "Rendering 404: #{exception.message}"
end
render :file => "#{Rails.root}/public/404.html", :status => 404, :layout => false
end