The :-moz-locale-dir(ltr)CSSpseudo-class matches an element if the user interface is being displayed left-to-right. This is determined by the preference intl.uidirection.locale (where locale is the current locale) being set to "ltr".
readyState should be used sparingly; L10n.ready() and L10n.once() are usually better suited for controlling when code is run relative to the state of the localization.
The :-moz-locale-dir(rtl)CSSpseudo-class matches an element if the user interface is being displayed right-to-left. This is determined by the preference intl.uidirection.locale (where locale is the current locale) being set to "rtl".