Microsoft's helping out the non-Internet Explorer browser.
The next web video standards, particularly in HTML5, are not totally united. While the many of the browsers support H.264, such as Safari and Internet Explorer, Mozilla has chosen to not use H.264 due to its potential patent fees (even though it's supposed to be license-fee free for the foreseeable future).
This means that Firefox, the most popular 'alternative' browser, doesn't support what could be the most popular form of HTML5 video. While it's admirable that Mozilla is sticking to its guns for a long-term vision, those wanting to use Firefox H.264 could be disappointed – if it weren't for Microsoft.
In a very surprising move, Microsoft has created a plug-in for Firefox that enables H.264 video playback on Windows 7 machines thanks to a trick that uses Windows Media Player.
From the release notes: "The extension is based on a Firefox add-on that parses HTML5 pages and replaces video tags with a call to the Windows Media Player plug-in so that the content can be played in the browser. The add-on replaces video tags only if the video formats specified in the tag are among those supported by Windows Media Player. Tags that contain other video formats are not touched."
If you're a Windows 7 user with Firefox 3.6 or newer, grab the download here.