net-stumble
To unexpectedly encounter something surprising/disturbing/intriguing while surfing the Internet. The key is the unexpected - if you were actively searching for "puppies on bicycles", finding "puppiesonbikes.com" does not count as a net-stumble.
Check this site out - it's like IMDB for adult film stars. I net-stumbled on it after mistyping the address of IMDB.