A term used on imageboards and forums to describe users and members who have been there from the start.
With regards to /b/, they're the only reason /b/ existed long enough for the newfags to ruin it. We don't want to explain memes to you or guide you away from the trolls. If you don't want to be called a newfag, then sit back idly until you're accustomed to our way of life. Then, an hero.
NF: /b/oxxy is our queen.
OF: Sage. Right fucking now.
NF: Stfu oldfag!
An Oldfag (also known as Elitist Asshole) is a user of an online community who has been with the community a considerable amount of time and won't shut up about it. Much like the old men that hang out in front of the liquor store, Oldfags harp on and on about the good old days and how things used to be. Oldfags generally consider themselves better than everyone one else, sometimes even people outside the community, because we all know being a member of Newgrounds or Deviantart for six years makes you a winner in the real world. Some Oldfags become even more Oldfaggy by harassing noobs if they dare to speak. It is possible to be a helpful senior member without being an Oldfag.
The opposite of an Oldfag is a Newfag, both terms are used on imageboards like 4chan.
I would have asked for help with the frames problem, but the only ones who know anything are oldfags.