Printscreen is from Slovak Firefox

Not if that is the browser default otherwise to make changes beyond the default settings would require something like "userChrome.css" to make browser changes.

1. Hello WestEnd, how can I proceed with this changes? 2. The second question is, that on my new PC (WIN 10 64bit) with Firefox 65 in the option "All supported types" is empty into brackets. Thank you.

Here's some read on it.

https://www.howtogeek.com/334716/how-to-customize-firefoxs-user-interface-with-userchrome.css/

http://kb.mozillazine.org/index.php?title=UserChrome.css&printable=yes

But if the problem isn't related to any userChrome.css then you might have to uninstall all firefox and delete mozilla folder and reinstall again to see if something got installed wrong. But make sure to backup any bookmarks you made to restore them back.

I think that the website specifies what file types to accept.

• https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/file

Might could happen that ESET Antivirus blocking this upload?

Socko777 said

How I can change value (somewhere in Firefox) to "*.*" as a first option during choosing files for upload to web.

Just enter *.* in the Filename Box or if you know the beginning part of a file, enter in ABC*.* or if you know the image type, enter ABC*.PNG or *.PNG or a text file as *.TXT and so on.

~Pj