the longest chain of distinct websites? or just the longest chain of websites, disregarding whether you've already visited some of them? if the latter, theoretically infinite, as many johnvertisements were not provided with a link upon submission and as such link back to, which itself has a johnvertisement, and thus one could theoretically cycle between and websites with a johnvertisement that links back to ad infinitum. you'd have to be infinitely lucky though, as some johnvertisements link to websites that are not, and you might end up at a dead end that way. if the former, I'd need data on the nature of johnvertisement links and some time to do some hypergeometrically distributed calculations.