Twitter is Down: Return of the Fail Whale on May 13, 2011
Is Twitter is Down? Yes. Twitter is Down. Get Back to Work
Twitter is down (May 13, 2011). Since it's Friday the 13th, you can blame Jason Voorhees, I guess. While twitter.com is not responding, my 3rd-party client (TweetDeck) is still updating.
This means that, while something has gone wrong with Twitter's website, tweets are still flapping through the bright blue sky that is the internet.
The situation seems to be improving: instead of pageload timeouts, now we at least get a Fail Whale with "Twitter is over capacity". Twitter has acknowledged "site stability issues" and is no doubt trying to sort the problem out ASAFP.
A good site to keep bookmarked is Down for Everyone or Just Me, though it only works when a site is totally borked, and doesn't register stuff like theming disasters.
[Update: Twitter's back, though pages sometimes still load as blank beneath the masthead, which has been an issue for a while now]