Please reboot your device by pulling out the battery (if this is a phone) and put the battery back in (if applicable) or turn it off (if this is a tablet) and turn if back on and check if Firefox is set as default and if not, try again. If you are still having trouble please provide the following:

Android version:
Firefox Browser version:
Device manufacturer and model:

Thanks!

any other suggestions?

Moving information from: https://support.mozilla.org/en-US/questions/968628

Android version 2.3.6 Firefox browser version 23.0 Device manufacturer Samsung Model# SCH-R760

What error message do you get? Could you provide the steps you are using to perform doing this?

I go into settings. open applications amd select all. scroll down to nrowser and open. scroll to default and its shaded saying no default setting.