The tweet reads "Experiencing site outage across all Wikimedia projects, including Wikipedia. Operations team is working on the issue."
According to Wikimedia head of communications Jay Walsh, the outage began just a couple minutes ago. "We're waiting for more details, but [operations] folks have been working on it," said Walsh.
Update: Just a few, short Wikipedia-less minutes later and Walsh says the site is back online. According to Walsh, Wikipedia generally experiences a 99% uptime. You can go back about your previously scheduled Web browsing...or read this selection of favorite Wikipedia articles on ReadWriteWeb:
Wikipedia Goes 3D - Wikipedia recently traded in its flat, 2D logo for a shiny 3D one, with special character sets and everything!
Why Wikipedia Should Be Trusted As A Breaking News Source - The news gathering process on our favorite, massively collaborative encyclopedia is quite impressive.
Somebody Broke Wikipedia - While downtime is not common for Wikipedia, it's not entirely unheard of. At least it was while all of the U.S. was out drinking beer and grilling stuff instead of looking for knowledge, right?
Wikipedians to Throw 300 Parties to Celebrate 10 Years of World-Shaking Knowledge Sharing - I'll be at the party in San Francisco this weekend. See you there?
For the super-technically inclined, you can keep track of the situation at @wikimediatech. We will update here as we find out more.
It appears that the site is working intermittently as it will load one time and not another. Looking at the logs for its Down Or Not page, it appears that the site may have been down for a total of 20 minutes, but is showing as back online now. Wikipedia itself has more than 400 million unique visitors each month and is the 5th most popular property on the Web.
While you're waiting, why not see what Wikipedia says it will look like in 10 years?