US Internet giant Google is to begin running advertisements along with video clips on its popular sharing website YouTube, according to a statement on the YouTube official blog.
The ads will run as "animated overlays that appear on the bottom 20 per cent of a video," said Google late on Tuesday, 10 months after the company bought YouTube for 1.65 billion dollars.
Although YouTube attracts nearly 190 million visitors per month, it has until now remained nearly free of advertising, and also revenue.
Internet users can ignore the overlay ads, close them or click on them to go to the advertiser's page.
The ads, which automatically pause the video, will appear within the first 15 seconds of the launch of a videoclip and end 10 seconds later.
Google said that it plans to post ads only on videos supplied by its official content suppliers, not on the amateur home videos which dominate the site.
Eileen Naughton, Google's director for media platforms, told the New York Times that Google would charge advertisers 20 dollars for every 1,000 times the ads were displayed.
The ads were to begin appearing from Tuesday throughout the site.