"YouTube's new ads involve a semitransparent, animated overlay that appears at the bottom of videos during the first 20 seconds of play and then disappears after 10 seconds. Consumers can close the overlay before it goes away or click on it to launch an ad, currently a video of any length or a flash-animation ad that can link to a Web page. The click-to-play ad pauses the video in a kind of voluntary commercial break, and the video resumes when the ad ends."

Link: http://money.cnn.com/news/newsfeeds/articles/djf500/200708212003DOWJONESDJONLINE000579_FORTUNE5.htm