A form was submitted in the %S encoding which cannot encode all Unicode characters, so user input may get corrupted. To avoid this problem, the page should be changed so that the form is submitted in the UTF-8 encoding either by changing the encoding of the page itself to UTF-8 or by specifying accept-charset=utf-8 on the form element.
Formular jo se w koděrowanju %S pósłał, kótarež njamóžo wšykne Unicode-znamuška koděrowaś, togodla by mógło zapódaśe wužywarja wobškóźone byś. Aby se toś ten problem wobinuł, by měł se bok změniś, tak až formular wótpósćelo se w koděrowanju UTF-8, pak pśez to, až změniśo koděrowanje boka do UTF-8, pak pśez to, až pódajośo accept-charset=utf-8 na formularnem elemenśe.