Mozilla has released an early test version of Firefox for Windows 8 that supports both the classic interface and the new modern interface. The current version only works on computers with x86 processors, so at the moment it does not work on tablets running Windows RT and ARM processors.
To download Firefox for Windows 8, go to nightly.mozilla.org and download the standard version. Once installed, you must set Firefox as the default browser for it to be activated in the new interface.
(via IDG News)