It means to be "Quoted For Notice".
Lets say you replied to some on a forum but didn't quote them. Some sites give notice when your quoted. So if you did not quote someone and desired an immediate response your next post should be. "QFN"
Stands for Quest for Narnia. A game played in some areas of Kansas. A game that it made up as you go. Very entertaining, and takes no skill.
"Hey Sam, after school you want to go play QFN? I'm really in the mood for a quest."