1 The most up-to-date version of Ruby on Rails Tutorial can be found on the book’s website at http://railstutorial.org/. If you are reading this book offline, be sure to check the online version of the Rails Tutorial book at http://railstutorial.org/book for the latest updates. In addition, PDF books purchased through railstutorial.org will continue to be updated as long as Rails 3.0 and RSpec 2.0 are still under active development.
2 RailsSpace, by Michael Hartl and Aurelius Prochazka (Addison-Wesley, 2007).
3 URL stands for Uniform Resource Locator. In practice, it is usually equivalent to “the thing you see in the address bar of your browser”. By the way, the current preferred term is URI, for Uniform Resource Identifier, ...