This is some feedback for rubyonrails.org. My apologies if this is the wrong forum to bring this up, but I wasn’t able to find a “Contact us” link on the site.
As of this writing, if I go to Google and search for “active record observer validations”, the top 2 results are:
http://guides.rubyonrails.org/active_record_validations_callbacks.html
and
http://api.rubyonrails.org/classes/ActiveRecord/Observer.html
If I follow either link, I get nginx’s default 404 page.
It appears both sites have been updated to refer to Rails 4, and the new URLs should be:
http://guides.rubyonrails.org/v3.2.13/active_record_validations_callbacks.html
and
http://api.rubyonrails.org/v3.2.13/classes/ActiveRecord/Observer.html
I recommend adding 301 redirects to those pages that don’t have a Rails 4 equivalent, and would generate a 404. Otherwise you’ll end up with a lot of people with broken bookmarks, as well as confused search engine users.
Jon