On some supported devices, a bug prevents Firefox from appearing in the Market. This is related to the recent Market update. You can go to Settings/Applications and uninstall the Market update, then find and install Firefox. Or, if you have a compatible device, 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 has removed the option to install from non-Market sources.) Also, Firefox will not appear in the Market on phones with incompatible hardware. You can check if your phone is supported here: https://wiki.mozilla.org/Mobile/Platforms/Android