Not really. (Score 2, Interesting)

As _xeno_ and others have said, the Avenue A site will take any query for the file name ("apple_g4_powerbook," "apple_g5_powerbook," "mango_juice" etc.) and dump a transparent GIF. So it's impossible to tell whether Avenue A had it configured specially for the apple_g5_powerbook keyword, or the other one, or it's just set up to track all queries it's asked for. According to ThinkSecret Apple is soon upgrading its Pbook G4 model, which would explain why they're adding stuff about it. Probably the Apple employee who added that code was lusting after the G5 and couldn't control his fingertips ;)