how (and where) is implemented validation errors in forms

nico itkin wrote:

I can't get information by myself when i need to understand rails "inside" mechanisms, if one of you can provide me some links which describe how rails is built, it would be really nice !!




This isn't an "inside" mechanism. You can write your own custom validations. Take a look at ActiveRecord::Validations::validate() in the rails api or do a google search on rails validations to find tons of tutorials on how to do this..