Context: In January 2010, YouTube launched an experimental version of the site that used the built-in multimedia capabilities of web browsers supporting the HTML5 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 HTML5 trial. Only browsers that supported HTML5 Video using the H.264 or WebM formats could play the videos, and not all videos on the site were available.

Question: In 2010 youtube launched a version of its site that ran on what standard?
Answer: HTML5

Question: What was the main benefit from the switch to HTML5?
Answer: allowed videos to be viewed without requiring Adobe Flash Player

Question: How did users opt into the trial version of youtube's HTML5 site?
Answer: a page

Question: What format besides H.264 was playable with HTML5?
Answer: WebM

Question: When did HTML4 become standard?
Answer: Unanswerable

Question: What happened in January 2009?
Answer: Unanswerable

Question:  What format besides H.264 was playable with HTML4?
Answer: Unanswerable

Question:  What was the main benefit from the switch to HTML4?
Answer: Unanswerable

Question: When did YouTube launch a version of its site that supported the HMLT5 standard?
Answer: Unanswerable

Question: What was no longer required with the support of HMLT5?
Answer: Unanswerable

Question: What were browsers supporting in order to use the H.642 or WemB formats?
Answer: Unanswerable