What is "Consider register" a search engine? Did you install it? Can you change the default at about:preferences#search

Bookmark and use this; Download the Mozilla Search Reset {web link} This add-on is very simple: on installation, it backs up and then resets your search preferences and home page to their default values, and then uninstalls itself. This affects the search bar, URL bar searches, and the home page.

I do not know how to translate, it can be "Match case". Button is selected by default, and it should be permanently off.

Start Firefox in Safe Mode to check if one of the extensions (Firefox menu button/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox menu button/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

I restart in Safe Mode, and also the button is highlighted. It can be configured in the about:config?

Does the button change when you press it?

https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save

Note: Some software, like Advanced SystemCare with Surfing Protection, can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.

You can check the accessibility.typeaheadfind.casesensitive pref on the about:config page.

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

cor-el said

You can check the accessibility.typeaheadfind.casesensitive pref on the about:config page. You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

Thank you very much!!!!!!! That helped!!!!! It was a 1, I set 0! Everything is fine!

Many thanks to all for your help! :))))

You're welcome