(In reply to comment #1)
> This is a question of UI, but the preferences don't really change, do they?
>
Clicking twice on "Use blank page" sets the home page to "about:blank". The setting is not saved for the current browsing session, but it _is_ saved in prefs.js. Therefore, if the lock on browser.startup.homepage is released, the loaded URL on startup will be about:blank.
(In reply to comment #1)
> This is a question of UI, but the preferences don't really change, do they?
>
Clicking twice on "Use blank page" sets the home page to "about:blank". The setting is not saved for the current browsing session, but it _is_ saved in prefs.js. Therefore, if the lock on browser. startup. homepage is released, the loaded URL on startup will be about:blank.