Facebook users in many countries found themselves shut out of the social network site because of a server problem.
Users in the UK, US, Thailand and Mexico and other nations began reporting problems yesterday. Some could not log in and the site was unusually slow and glitchy for others.
Many used Twitter to complain.
Facebook spokesman Matt Hicks said it was a "small percentage of users" who had problems accessing Facebook, their friends' profiles or specific site features because of an isolated server problem.
At 11pm yesterday, Facebook said it had restored access to the users.
Facebook, which has more than 400 million users, has generally avoided such hiccups, but Twitter has had bigger problems. Last August, hackers shut down the short messaging service for several hours.
Facebook also experienced problems, but it was never shut down completely.