If you're trying to do the example in Chapter 5 that begins on page 137 in Ruby 2.0.2, you'll need to change "start_form_tag" to form_tag."
You can see the documentation for form_tag here:
http://api.rubyonrails.org/
You can see a handy list of methods that don't work after the 2.0 upgrade here:
http://www.slashdotdash.net/articles...-upgrade-notes
It would be really nice if the author of this book would post a list of things that won't work in 2.0 without changes to the book's code.