Open the Android "Settings" app. Tap on "Applications" then "Manage Applications." Tap on the "All" tab, then find Browser and tap on it. Under "Launch by default" press the "Clear Defaults" button. Now when you open a link, Android will ask which browser to use, and offer to set a new default.

Thanks, jakehouse95. That did the trick.

Tried this. Stock browser shows "No defaults set," thus cannot clear defaults. Firefox for Android shows same thing. How do you tell a Samsung Galaxy Tab 8.9 on Android 4.0.4 to make Firefox the default browser?

Never mind- I figured it out. Since no default was set for either browser, next time I went to a web page (via a link in Google Reader), it asked which browser to use, and there was a check box to set the choice as default. This was never presented before since the tablet previously had only one browser on it.

I think I found an alternate solution!!

I had followed the instructions above but my damn HTC Thunderbolt would STILL default to the built in browser. Then a student worker in my dept helped me figure it out!

>Settings >Applications >App Associations >Web URLs

You get a pop-up window that asks which browser you want, hit Firefox or your preferred one.

Hope that helps & no offense to previous posters!