http://builtwith.com/?http://answers.oreilly.com/
Says, PHP / Rails. Where as Stackoverflow is ASP.MVC.
I'd like to acknowledge the projects that have proceeded Answers and inspired us, such as SitePoint Forums (we distribute their books), StackOverflow, Yahoo! Answers, Knol, and many others
http://builtwith.com/?http://answers.oreilly.com/
Says, PHP / Rails. Where as Stackoverflow is ASP.MVC.