The microblogging site, Twitter, was out of commission for a couple of hours early on Sunday for some of the roughly 100 million users around the world.
Instead of the usual screen that allows people to send a tweet, the home page indicated the site was down for "planned maintenance" but was expected to be back in a few hours.
It was accompanied by a cartoon.
According to a status website run by the San Francisco-based company, Twitter's hosting provider, NTT America, was to start the maintenance at 2 am (local time) on Sunday and it was to last about five hours.
Some tweets appeared to start moving again after about 90 minutes but some users were still unable to send messages hours later.