Firefox 3.1 Beta release
This release is for experienced developers only, as in any beta offering. Pilot test only and don't use for production purposes.
Firefox 3.1 Beta release
http://www.mozilla.com/en-US/firefox/all-beta.html
Firefox 3.1 Beta Release Notes
http://www.mozilla.com/en-US/firefox/3.1b1/releasenotes/
US Download link
http://www.mozilla.com/en-US/products/download.html?product=firefox-3.1b1&os=win&lang=en-US
Note - Please be careful during the install, as FF 3.1b can become your default browser if you don't see and uncheck the default. If desired, IE 7/8 can be reset back as the default browser, as follows:
Tools >> Internet Options >> Programs >> Default Web Browser