Online encyclopaedia Wikipedia was unavailable for some of Wednesday due to technical difficulties with its servers.
The free encyclopaedia, which can be edited by anyone and built on Wiki software, suffered a power failure, a Wikipedia spokesman told ZDNet UK.
"A power outage — it's nothing more than that. It's something our technical staff are working on," said the spokesman. "It's nothing out of the ordinary," he added.
Attempts to access Wikipedia from the UK during Wednesday morning and early afternoon were met with an error message, which said that the problem was likely to be resolved soon.
"The Wikimedia Foundation servers are currently experiencing technical difficulties," said the message. "The problem is most likely temporary and will hopefully be fixed soon. Please check back in a few minutes."
By 1700 BST the site was back up, although it appeared to take longer to resolve search requests.
Wikipedia has increased in popularity since the beginning of the year, according to Web traffic ranking company Alexa.com. It is currently ranked 17th in the world for the amount of traffic it receives, and has been in the top twenty since the beginning of January.
The Wikipedia spokesman said there was the "distinct possibility" that the technical problems experienced by the site had been in part exacerbated by the amount of traffic it receives, but stressed that he would have to confirm this with technical staff.
"Wikipedia is now one of the most visited sites on the Internet by traffic and continues to grow, and as a result the Wikimedia Foundation has a constant need to purchase new hardware," said the error message.