"wrong username or password"

Translation: неверный логин или пароль

[Mutusen]

Can you say неправильный instead of неверный?

[JanisaChatte]

Yes you can. It is accepted now.

[shkrjab]

username — имя пользователя not логин!!!!

[Thom844913]

If the two words had different genders, which genders the adjective be?

[Shady_arc]

With или, the gender will match the first word and the adjective will be in the singular (if the first noun is in the singular, of course).

[MatejPavlk1]

Do russian people have original Russian words for "login", "site", "flashdisc" and other modern words, especialy words used in this course ?