Strange warning messages at the bottom of my site

[infokult]

Hello,

There are constantly 3 warning messages (all 3 together) at the bottom of my site infokult.altervista.org .
To solve the problem, I edited some css and php files to try to make the messages disappear, but nothing helped.

This problem started right after I tried changing the charset of my site (from utf-8 to windows-1250 and others).

After that, I set it back to UTF-8 again, but the same 3 warnings are still at the bottom.

I have used recovery mode and option "repair". The "repair" went ok and I thought all problems were solved, but this morning I have noticed the same 3 warning messages at the bottom.

As I can conclude, these 3 warning messages might be statically written in some file, but I cannot find where.
(Editing formatting.php file did not help)

The messages are:

Warning: htmlspecialchars(): charset `windows-1250' not supported, assuming utf-8 in /membri/infokult/wp-includes/formatting.php on line 3436

Warning: htmlspecialchars(): charset `ISO-8859-2' not supported, assuming utf-8 in /membri/infokult/wp-includes/formatting.php on line 3436

Warning: htmlspecialchars(): charset `ISO-8859-4' not supported, assuming utf-8 in /membri/infokult/wp-includes/formatting.php on line 3436

Thanks in advance!