Wikipedia is down. Confirmed on Twitter.
Update: Wikipedia Mobile is working fine.
Wikipedia has this latest update:
Due to an overheating problem in our European data center many of our servers turned off to protect themselves. As this impacted all Wikipedia and other projects access from European users, 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.
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, but unfortunately it may take up to an hour before access is restored for everyone, due to caching effects.
Wikipedia operators have confirmed that the service is down. There is a blog post about the downtime but we cannot access that as well.
Only the English language version is affected.
The problem is said to be related to DNS. So, some users might be able to access it still.
Wikipedia has been posting updates about the problems on their Twitter account.
Checkout: Wikipedia on Twitter