The outage struck down one of the world's most popular websites, the online encyclopaedia Wikipedia, is now over.

Earlier today its administrators said via Twitter that it was working on the problem, which is affecting users around the globe, and would provide more details when they were available.

The administrators later issued an update in which it said Wikipedia was "slowly" coming back online after a power outage affected its data centre in Florida.

Liam Wyatt, vice president of Wikimedia Australia, reported in his own Twitter feed that air conditioners at the data centre had failed, causing Wikipedia's servers to overheat.

"Wikipedia's down," wrote Wyatt. "Unfortunate timing just before Wikimania when most of the techies are traveling!"

Wikipedia, where users contribute and edit material, is used by most internet users as the first port of call for any online trivia request. It does, however, often attract criticism for its perceived unreliability.

Wikipedia was launched by American entrepreneur Jimmy Wales in 2001 with the idealistic intention of being an online repository of all human knowledge.

One of Wikipedia's founding principles - that any user could update or add to information - was abandoned last year due to a growing problem with vandalism.

Wales has previously stated he wanted to get the message out to students that they shouldn't use it for class projects or serious research, according to an article in the Chronicle of Higher Education.

The Chronicle quoted Wales telling a conference in the United States that he got about 10 emails a week from students who complained that Wikipedia had gotten them into academic hot water.

"They say, 'Please help me. I got an F on my paper because I cited Wikipedia', and the information turned out to be wrong."

But he had no sympathy for their plight. "For God's sake, you're in college; don't cite the encyclopedia."

Comments on today's outage are running hot on the Twitter social networking website.

* "Wikipedia's down. I feel odd, as if I just lost 99.999 per cent of the information from my fingertips for a few minutes"

* "Strange - Wikipedia appears to be down. Never known this before. That's like Google being down!"

* Wikipedia can't be down on Independence Day! That'd be an American tragedy! Wait, is Wikipedia American? I need to look that up. Oh,wait...

* Wikipedia is down, great. I NEED to find out the names of the members of ZZ Top and which one guest starred on Bones.

* New alert: Wikipedia is down. Uni students everywhere requesting extensions on essays.

* oh em gee, wikipedia is down. how am I to refresh my store of useless trivia now?

* You never realize how much you take Wikipedia for granted until it's down

* Wikipedia is down. The riots will soon begin. Chaos will soon reign as people find out that their friends aren't actually smart.

Read the latest discussions on the Wikipedia outage here.