It is the retarded and incorrect way of spelling "In Fact". It is a common misconception like "alot".
Friend 1: Hey mate you here about that new iPhone?
Friend 2: Yea the iPhone 5?
Friend 1: Yea the fifth in series.
Friend 2: Well you may think it is the iPhone 5 but infact it is actually the sixth in the series.
Friend 1: Yea well... Fuck you that's what.
Friend 2: Owned.