Wikipedia and other Wikimedia Foundation Web sites went down for hours on Wednesday in a global outage caused by a domino effect of technical problems.

The problems started when Wikimedia servers overheated in the organization's European data center and shut themselves off automatically.

Wikimedia then switched all its traffic to its server cluster in Florida, but the failover process, which involves changing servers' DNS entries, malfunctioned, knocking the organization's sites offline around the world.

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