Wikipedia and YouTube have both experienced outages over the last twenty-four hours.
YouTube was failing to show its home page for about an hour and a half, although links to individual videos still worked. The front page simply showed a Http/1.1 Service Unavailable or 500 Internal Server Error message.
There's no word yet from Google on what caused the problem, which started about 7.00 am EST and cleared up at about 8.30.
And Wikipedia had similar problems yesterday. According to its blog, the failure was caused by overheating at its European datacenter in Amsterdam, which caused many servers to turn off.
"we were forced to move all user traffic to our Florida cluster, for which we have a standard quick failover procedure in place, that changes our DNS entries," said the blog.
"However, shortly after we did this failover switch, it turned out that this failover mechanism was now broken, causing the DNS resolution of Wikimedia sites to stop working globally. This problem was quickly resolved."
The crash started at about 1.00 am EST yesterday, and was pretty much resolved within two hours. However, says Wikipedia, there's still a bit of overheating, so some users may continue to have problems.