AS the nation marked this terrible anniversary, people invariably turned to Wikipedia to learn about the events of Sept. 11, 2001. Nearly two million page views were registered last September for the article “September 11 Attacks,” a typically Wikipedian effort with exhaustive, even picayune, details of the events, bolstered by nearly 289 footnotes. This September, the total page view number could be something like six million.

Likewise, readers have repeatedly turned to the article “9/11 Conspiracy Theories.” The article — similarly detailed with 299 footnotes purporting to explain accusations of faked video footage or controlled demolition of the two buildings — had 400,000 page views last September, and is on pace to have more than a million views this year.

One thing is certain, however. Not one of those visitors got to the conspiracy theories page by making a hypertext leap from a link in the main article about the Sept. 11 attacks. There is simply no mention of these theories, deemed fringe ideas, which have been repeatedly and officially discredited. They are written up in a variety of articles on Wikipedia, but they are kept on the fringe of the site.

This is no accident, but rather a Wikipedia policy concerning a topic as fraught with emotion as the Sept. 11 attacks. Thus the so-called gatekeepers of the media world — prominent newspapers, television news programs, newsweeklies — have an unlikely ally in Wikipedia, which bills itself as the encyclopedia anyone can edit.