It appears IGN Movies has solved the riddle left by Warner Bros. on the teaser site promoting the next Batman movie, The Dark Knight. As the reward, we get to see not only Heath Ledger as the Joker, but also a video teaser of the movie as well.
The Dark Knight is the sequel to the series reboot, Batman Begins, starring Christian Bale as the masked crusader. Bale and Ledger will be joined by Maggie Gyllenhaal (Rachel Dawes), Gary Oldman (Lt. Gordon), Aaron Eckhart (Harvey Dent), and, of course, Michael Caine (Alfred). The movie is scheduled for a summer 2008 release.
Source: IGN Movies