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.
Use of Ogg formats in HTML5
CTO at Opera Software, Håkon Wium Lie explained in a Google tech talk entitled "The  element" the proposal of Theora as the video format for HTML5:
After the presentation, Lie was asked whether Opera will support other formats than Ogg: