We have been building a version of Firefox for Windows Mobile for quite a while, with the expectation that Microsoft would be doubling down in the mobile market and hoping that they would put out a great new mobile operating system. We’ve been following the Windows Phone 7 announcements quite closely for the last few weeks, and had one of our developers in attendance at MIX last week. We know that the underlying platform for Windows Phone 7 is Windows CE 6, which is a big step up from the kernel used by Windows Mobile 6.5. Windows CE 6 is a platform that we have been developing towards, and already run well on, leaving us well positioned to have an awesome browser on Windows Phone 7.

While we think Windows Phone 7 looks interesting and has the potential to do well in the market, Microsoft has unfortunately decided to close off development to native applications. Because of this, we won’t be able to provide Firefox for Windows Phone 7 at this time. Given that Microsoft is staking their future in mobile on Windows Mobile 7 (not 6.5) and because we don’t know if or when Microsoft will release a native development kit, we are putting our Windows Mobile development on hold.

The work on this project that the community and our engineering, QA, build, and automation teams has done has been great. I expect us to be able to use much of the knowledge and work for other platforms. We will be disabling the builds and test automation shortly, and developers shouldn’t worry if the tree breaks.

While I hope that we do see Microsoft provide us with a way to build Firefox for Windows Phone 7, we will continue to focus on the things that we can control: building a great consumer product on both Android and Maemo.
Source from a Mozilla Blog
Stopping Development for Windows Mobile blog.pavlov.net