HTML and CSS Reference
Older browsers, such as IE 7 and IE 8, get the YouTube video, which ensures that web page
readers using these older browsers have access to the material. However, if you remove the
Ogg Vorbis and WebM source elements and open the page in Firefox, all you'll get is a square
gray box with a lighter gray X because Firefox can't find a video source it can play. You won't
get the YouTube video.
The only way to ensure that a video plays in all of the target browsers and other user agents is
to provide all the appropriate video types.
Before getting into the codecs, it's important to know that you can use video files with an audio
element, and audio files with a video element. The only difference between the two is the video
element provides a playing area. All browsers support video files with the audio element, but only
Opera and Firefox currently support audio files playing in the video element. I strongly recommend
using the appropriate element.