I was wondering why my post was migrated to Super User?
Generally, what kinds of web application questions belong here and what belong to Super User?
Web Applications aren't installed on your computer and tend to run only in your browser.
Your question was about how to configure Firefox, which is a program that is installed on your computer. This is the domain of Super User.
Firefox is not a web app and hence questions about it are generally suited to the site that does deal with software and hardware issues like that.