This site might help you: https://support.mozilla.org/en-US/kb/settings-fonts-languages-and-pop-ups?redirectlocale=en-US&redirectslug=settings-fonts-languages-pop-ups-javascript Do you have the English version? You could try uninstalling, downloading, and reinstalling Firefox? You could also try deleting your cookies. "Some web pages are offered in more than one language. Click the Choose… button to specify your preferred language or languages."