Designed and developed by parent company HBO, companion websites were part of HBO's elaborate viral marketing campaign used to establish viewership.
Targeted to a global audience, the websites provided bonus material that sometimes took a behind-the-scenes approach in their delivery.
The banners below were used as billboards along the roadside in big cities.
Themes included cologne to help vampires attract a human, job listings for mainstreaming vampires, and even motorcycles to help a vampire "outrun the sun".
Series creator Alan Ball had previously worked with premium cable channel HBO on Six Feet Under, which ran five seasons.
In October 2005, after Six Feet Under's finale, Ball signed a two-year agreement with HBO to develop and produce original programming for the network.
At least two websites were created by movie producer/distributor Twentieth Century Fox.
They are listed for archival purposes, as they come from an official source.
Users could play games or watch videos and receive codes, followed by a message saying they were either a "winner" or "loser" of an Instant Win prize.
Websites and their resources must be maintained, and their cost to exist usually isn't cheap.
For this reason, many companies will delete the companion website, usually within the first five years after the product complemented is no longer on the market.
Each time a video was watched, one entry into the contest's larger drawing, for cash or larger prizes, was submitted, and losing an Instant Win did not disqualify a user's chance at winning the larger prize.
Season 6 introduced several new companion websites, based on HBO's desire to modernize their image.