Since FF 24 and also in 25 & 26 it keeps loosing the customisation of controls after new start or updates.
I always do this: "Customize navigation buttons like back, home, bookmarks & reload" - http://mzl.la/LqHj2n.
When I updated from 23 to 24/25/26 or have a FF crash in any of these versions, the customisation is back to default. I hate to redo this every time!
Go to Solution.
What is your Operating System?
You can check for problems caused by a corrupted localstore.rdf file.
@cor-el: My OS - I have OSX 10.8.5 on a MBP
Your suggestion to rename the localstore.rdf file (for Mac "~/Library/Application Support/Firefox/Profiles/xxxx0000.default/localstore.rdf) seems to solve the problem.
When I open a new window, now the customisation is remembered again. Will check after an update or crash and report here again ...