Thousands and possibly millions of websites hosted by GoDaddy.com are down.
A hacker is claiming responsibility, but the real reason for the outage is unclear.
A Twitter feed allegedly affiliated with the Anonymous hacker group says it's behind the outage, but another Twitter account associated with Anonymous says the first one is just taking advantage of an outage it had nothing to do with.
GoDaddy.com hosts more than five million websites, mostly for small businesses.
Websites that were complaining about outages on Twitter included YouWatch.org, a video sharing site.
GoDaddy issued its own statement on Twitter: "Status Alert: Hey, all. We're aware of the trouble people are having with our site. We're working on it."