NEW YORK (AP) - Facebook was inaccessible to many users Thursday afternoon, with people getting error messages and as "DNS Failure" pages when they tried to visit the website.
Facebook, which has 500 million users worldwide, said it is "experiencing some site issues," which is causing Facebook to be slow or unavailable for some users.
"We are working to resolve this issue as quickly as possible," the company said in a statement.
Users in the U.S., Europe and South America were experiencing problems, but they seemed to last only about an hour.
Facebook users were also experiencing intermittent problems accessing the site on Wednesday, but spokeswoman Meredith Chin said the problems on Thursday were unrelated.
The site has generally been reliable, with few network problems.
The Facebook outage came two days after a mischievous hack spread through Twitter, the short messaging site. That attack didn't shut Twitter down but it spread "tweets" of blocked-out text to people's accounts, causing pop-up windows to open on their computer screens.