Currently the mobile Firefox is only for Android 2.0+ (and ARMv7 cpu's) and Mamo and Meego.

https://wiki.mozilla.org/Mobile/Platforms#Other_Platforms

Windows Mobile
   Firefox has stopped development for Windows Mobile indefinitely. Thank you to our contributors for their continued support and feedback. The last release for Windows Mobile was 1.1 alpha 1 (download). We have stopped developing for Microsoft's mobile platform because Windows Phone 7 no longer allows developers to build C++ applications like Firefox, and Microsoft's new policies ban open-source software like Firefox from the Windows Phone Marketplace.

thank you, James

Please click the Solved It button next to the answer that answered or solved your Firefox support issue, it appears when you are logged in, so this thread gets marked as Solved to help other users who may have this same problem.