Removing Web access from Firefox

I am a network administrator for a state's department of corrections. We have need to have present an HTML reader or offline browser for use by inmates. Our security policies do not allow the users to access the Internet directly. We are looking for an open source solution (Firefox?) but need help in understanding how to toggle certain fuctionality off or hiding it from user views and access. (most drop down menus, most dialoge boxes, etc). I found an article partially describing accessing config and working with preferences but need more detailed info.