You can check that those pages aren't set as multiple homepages.

You can check the homepage setting.

• Options/Preferences -> Home
• https://support.mozilla.org/en-US/kb/how-to-set-the-home-page

Firefox supports multiple homepages separated by '|' (pipe) symbols.

You can check that those pages aren't set as multiple homepages. You can check the homepage setting.

• Options/Preferences -> Home
• https://support.mozilla.org/en-US/kb/how-to-set-the-home-page

Firefox supports multiple homepages separated by '|' (pipe) symbols.

I mean page like this one https://www.mozilla.org/en-US/firefox/welcome/1/ and several others

Pages like that can still be part of the homepages, but it is also possible that there is a problem with the file that stores the preferences and that Firefox thinks that it has updated.

You can check for problems with preferences. You can delete possible user.js and numbered prefs#-##.js files and rename/remove the prefs.js file to reset all prefs to the default value including prefs set via user.js and prefs that are no longer supported in current Firefox releases.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

Pages like that can still be part of the homepages, but it is also possible that there is a problem with the file that stores the preferences and that Firefox thinks that it has updated. You can check for problems with preferences. You can delete possible user.js and numbered prefs#-##.js files and rename/remove the prefs.js file to reset all prefs to the default value including prefs set via user.js and prefs that are no longer supported in current Firefox releases. You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

I use autoconfig.cfg only, its new way set prefs in modern versions FF

I'm using autoconfig.cfg as well.

Note that it isn't always necessary to use lockPref() as in a lot of cases pref() or defaultpref() is sufficient.

• https://support.mozilla.org/en-US/kb/customizing-firefox-using-autoconfig

I'm using autoconfig.cfg as well. Note that it isn't always necessary to use lockPref() as in a lot of cases pref() or defaultpref() is sufficient.

• https://support.mozilla.org/en-US/kb/customizing-firefox-using-autoconfig

you mean this pref?

browser.startup.homepage = about:home

or

• startup.homepage_override_url

or

• startup.homepage_welcome_url = about:welcome