I tried this and it did not take me back to the page I originally came from.

For ex:

I am learning to use authlogic, and I am at controller called animals. So I click register link on that page, and registered successfully, but it did not go back to that page I came from. Instead I got the error:

undefined local variable or method `root_url’

so I changed my root url to controller animal, and it took me back to my welcome page, instead of the page I needed to see my flash notice “Registration Succesful”