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I uploaded the screenshot again

In case you use "Clear history when Firefox closes" or otherwise clear history.

• do not clear the Site Preferences

• Tools > Options > Privacy > Firefox will: "Use custom settings for history": [X] "Clear history when Firefox closes" > Settings
• https://support.mozilla.org/kb/remove-recent-browsing-search-and-download-history

• Clearing "Site Preferences" clears all exceptions for cookies, images, pop-up windows, software installation, passwords, and other website specific data.

hello. i dont clear history and Site Preferences. i just close firefox and open it again and new firefox page opens with % 100 zom.

when i restart firefox remembers all of my passwords. cookies and web history stays there. Site Preferences looks same except zoom setting.

You can look at the Default FullZoom Level or NoSquint extension to set a default font size and page zoom on web pages.

• Default FullZoom Level: https://addons.mozilla.org/firefox/addon/default-fullzoom-level/
• NoSquint: https://addons.mozilla.org/firefox/addon/nosquint/

If you use cleanup software like CCleaner then check the settings for the Firefox application.

There is software like Advanced SystemCare with its Surfing Protection feature that can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.

ok it worked.thank you very much for help

You're welcome