config.consider_all_requests_local  = false    # rails 4.0

config.action_controller.consider_all_requests_local = false  # rails 3.0

 # make sure this rule is the last one
get '*path' => proc { |env| Rails.env.development? ? (raise ActionController::RoutingError, %{No route matches "#{env["PATH_INFO"]}"}) : ApplicationController.action(:render_not_found).call(env) }

 1  def self.rescue_errors
 2     rescue_from Exception, :with => :render_error
 3     rescue_from RuntimeError, :with => :render_error
 4     rescue_from ActiveRecord::RecordNotFound, :with => :render_not_found
 5     rescue_from ActionController::RoutingError, :with => :render_not_found
 6     rescue_from ActionController::UnknownController, :with => :render_not_found
 7     rescue_from ActionController::UnknownAction, :with => :render_not_found
 8   end
 9 
10   rescue_errors unless Rails.env.development?
11 
12   def render_not_found(exception = nil)
13     render :file => "/public/404.html", :status => 404
14   end
15 
16   def render_error(exception = nil)
17     render :file => "/public/500.html", :status => 500
18   end