YouTube already supports uploads of 1080p, but users have only been able to watch them in 720p. Beginning next week, users will be able to watch in 1080p. Google said that 1080p videos that have been uploaded already will be re-encoded by Google so that they show in the correct 1080p resolution.
When users visit any given video, if a high resolution version has been uploaded, they need only click the "HD" link, which appears on the right side of the tool bar below each video. The high quality version of the video will then play.
Want a taste? Follow this link to see the trailer for Disney's Toy Story 3.