When Mike and Mark are talking about girls, MIke says whenever you make out with a girl put on side one of Led Zeppelin 4. But in the next scene where Stacy and Mark are in the car "Kashmir" is playing. "Kashmir" is side one of Physical Graffitti. Wrong album.
It's deliberate, in order to make Mark look dorky.
It was originally meant to be correct, but when Cameron Crow couldn't obtain the rights to the song, it was played to make Mark look incompetent.