Firefox 4 Web Browser Beta Release Announced by Mozilla
Firefox 3.0 was released two years ago, while version 3.5 came out in 2009. This recent release includes the Websocket API, which allows web-based applications to access servers using additional protocols.
Most interesting for developers, this release includes support for HTML 5 video playback using the Google WebM video codec, which is also open source. The beta release can be downloaded from Mozilla's website.