When you are surfing the web and you keep clicking on links bouncing from page to page to page or using a search engine to find something else you stumbled upon. You eventually wind up far from where you started.
I was reading a story about Obama and somehow ended up on a page about circus clowns because I was linkhappy.
To click on one link and to be brought to that page, only to find another interesting link on that page and end up clicking on that. This is a common thing that happens on sites like wikipedia and imdb.
Todd got on a link tangent on wikipedia by starting to read about the Spotted Owl and ended up reading about Jackie Chan.