Wikipedia experienced major service outages today that took the popular free reference site down for roughly 2 hours, beginning at around 1:00 PM EST.
According to a Facebook blog post, the outage has been attributed to overheating at the site's European data center.
The servers shut down, which ultimately led to more issues:
"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," the site said in a statement. "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.
Wikipedia resolved most of the problems by 3:00 PM EST, according to the site's official Twitter account. Due to continued overheating at the Amsterdam data center, however, users may still be experiencing service glitches.
Wikimedia Foundation.

From approximately 1:00 p.m. (18:00 UTC) to 4:00 p.m. (22:00 UTC) Eastern Standard Time (EST), the popular free encyclopedia Wikipedia, alongside its sister projects (including Wikinews), went offline due to major server outages. Downtime was later attributed to overheating at the Project's central data center in Amsterdam. 

According to a post made by Mark Bergsma at the Wikimedia Foundation's  technical blog, the servers "shut themselves down" to avoid further heat damage.

Administrators reportedly attempted a shift of traffic to the Project's servers in Florida. However, "it turned out that this failover mechanism was now broken, causing the DNS resolution of Wikimedia sites to stop working globally."

According to the Project's official Twitter account, programmers were able to resolve most of the server problems by around 4:00 p.m. EST. Since the situation with the servers in Amsterdam is still ongoing, some users may still experience lingering service glitches due to "caching effects".