linux store most of settings in personal folder. If you want to remove rest of data than:
1. open xterminal
2. type: ls -a
You will see all files and folders even hiden. if you want more information type: ls -la |more
if in line first letter "d" it is mean folder.
Mozilla store all settings in folder .mozilla
3. for remove all data from broser type: rm -R .mozilla
it will remove all mozilla settings. when you will start browser next time it will be like new.
most other programs store settings in similar folders (.name)
Just remove them and reboot.

flash which you did remove all installed by you programs but don't remove settings

good luck