Bugs
Here you can find the bugs found out thanks to the messages sent by the visitors by using the Feedback section.
Firefox preferences and locale code
A subset of the Firefox preferences uses placeholders like %LOCALE% for the language code defined by the general.useragent.locale preference (for its values, see the Change language section). The default preference extensions.blocklist.detailsURL, for example, is:
http://%LOCALE%.www.mozilla.com/%LOCALE%/blocklist/
When the value of %LOCALE% is roa-IT-ins you obtain some errors, because URLs like the following don't work:
http://roa-IT-ins.www.mozilla.com/roa-IT-ins/
blocklist/
To avoid issues, the langpack changes directly the default preferences using placeholders like %LOCALE% to hard-code the value it. If you disable or remove the langpack, the values will be the default ones.