How to show "Messages" at the top of certain nodes ?

Well I am looking for some kind of input format filter which can show wikipedia style messages like "This Node can not be edited " or "This Node can only be edited by registered users" or "This page has factual errors" etc.

Ofcourse I can manually too do this by entering the words at the Top or bottom of the page but I am looking for something more clean way of doing it.