Does this help Navigation buttons like back, home, bookmarks and reload are missing

thanks, Restore Default Set does help~ but the next time when I open firefox the problem appears again :(

Is firefox still crashing now ?

Did you read further in the linked article, the suggestions after, Restore Defaults, are troubleshooting add-ons, and resetting the controls & toolbars whilst in safe mode.

Similar advice is given in : Changes to toolbars and window sizes are not saved

Ya, I did followed "resetting the controls & toolbars" and fixed it, and I don't think this is due to my add-ons/extensions since I didn't add any new one to firefox these days but just updated to the latest version. Somehow the problem is now fixed, but sometimes whenever you move or make changes on the toolbar settings/buttons, it crashs again. That makes me have no choice but to set everything from the begining again.

Thanks anyway :)

If you are happy to continue repeatedly restoring settings you need do nothing else.

However this should not happen. Also if firefox is crashing you may wish to investigate that also. To start off with it may be worth reading firefox crashes one thing that would need determening is exactly when firefox crashes, and confirmation that it is a crash rather than a hang.

• see also firefox hangs