Wikipedia, one of the 10 most popular sites on the Web, was founded about eight years ago as a long-shot experiment to create a free encyclopedia from the contributions of volunteers, all with the power to edit, and presumably improve, the content.

Now, as the English-language version of Wikipedia has just surpassed three million articles, that freewheeling ethos is about to be curbed.

Officials at the Wikimedia Foundation, the nonprofit in San Francisco that governs Wikipedia, say that within weeks, the English-language Wikipedia will begin imposing a layer of editorial review on articles about living people.

The new feature, called “flagged revisions,” will require that an experienced volunteer editor for Wikipedia sign off on any change made by the public before it can go live. Until the change is approved  or in Wikispeak, flagged  it will sit invisibly on Wikipedia’s servers, and visitors will be directed to the earlier version.