See this support article: <br /> https://support.mozilla.com/en-US/kb/will-firefox-work-my-phone#os=android&browser=m4

Firefox will not appear in the Market for most phones with incompatible hardware. You can check if your phone is supported here: https://wiki.mozilla.org/Mobile/Platforms/Android Even on some supported devices, a bug in the Market software prevents Firefox from showing up. This may be related to the fairly recent Android Market app update. If you go to Settings/Applications/Market and choose "Uninstall" you can uninstall the update, and then search for and install Firefox from the marketplace. Or, if you have a supported phone, you can download the app directly from here: http://ftp.mozilla.org/pub/mozilla.org/mobile/releases/4.0b3/android-r7/multi/ (Note: To download the app directly for an AT&T phone, you will have to search for instructions on "sideloading" the APK file, since AT&T disables the option to install from non-Market sources.)