Routing Error Ruby on Rails
===

I've installed ruby on rails 3.2.6, and when i execute 
     **rails server**

and acces to 127.0.0.1:3000 it works, but when i generate a controller, for example

**rails generate controller principal**

and acces to 127.0.0.1:3000/somecontroller, browser show following error:
Routing Error

**No route matches [GET] "/principal"
Try running rake routes for more information on available routes.**

what i need do more?
what's wrong?

thanks in advance
