Use of Ogg formats in HTML5
, HTML5 video is not currently as widespread as Flash videos, though of recent rollouts of experimental HTML5-based video players on websites, DailyMotion is so far the only one to use Ogg Theora and Vorbis formats, which suggests an increasing early interest in adopting HTML5 video.
Adobe Flash
Representing open standards, inventor of CSS and co-author of HTML5, Håkon Wium Lie explained in a Google tech talk of 2007, entitled "the  element", the proposal of Theora as the format for HTML5 video:
I believe very strongly, that we need to agree on some kind of baseline video format if [the video element] is going to succeed. Flash is today the baseline format on the web. The problem with Flash is that it's not an open standard.