Just few days after the arrival of "The Dark Knight" teaser page on the web, the site has already been updated with a new image showing Aaron Eckhart as Harvey Dent, a close ally of Batman besides Lieutenant Jim Gordon before the acid incident turns him into supervillain Two-Face.
The image can be viewed either by clicking the Batman logo on the site or simply going to IBelieveinHarveyDent.com. Its appears to be a kind of political campaign hailing Dent for the seat of Gotham City's district attorney.
Further, the official site's source code also turns out to include the synopsis for the flick, telling that the caped crusader "sets out to dismantle the remaining criminal organizations that plague the city streets" with the help of both Gordon and Dent. Though the "partnership proves to be effective", the three soon "find themselves prey to a reign of chaos unleashed by a rising criminal mastermind known to the terrified citizens of Gotham as The Joker."
UPDATE 05/21/2007: In addition to the link showing the image of Harvey Dent, Warner Bros. has also released a site made by the Joker, IBelieveinHarveyDentToo.com. The site contains a defaced Harvey Dent image, which then reveals underneath the first photo of the super-villain, played by Heath Ledger.