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.)

firefox for android 1.5 is not available.where is it? don't lose your clients.

than, armv7 processors 1ghz?? are u crazy..and others phones with 500+ mhz..hm.

Try visiting http://firefox.com/m in your phones browser if you can't find Firefox in the market.