In January 2010, YouTube launched an experimental version of the site that used the built-in multimedia capabilities of web browsers supporting the <answer>HTML5</answer> standard. This allowed videos to be viewed without requiring Adobe Flash Player or any other plug-in to be installed. The YouTube site had a page that allowed supported browsers to opt into the <answer>HTML5</answer> trial. Only browsers that supported <answer>HTML5</answer> Video using the H.264 or WebM formats could play the videos, and not all videos on the site were available.
In 2010 youtube launched a version of its site that ran on what standard?
HTML5