Wikipedia, the open online encyclopedia that's written and monitored by volunteers, has changed its rules for submitting articles after a posting incorrectly linked the assassination of Robert F. Kennedy to a former administrative assistant.

A May 26 posting on John Seigenthaler Sr., an assistant to the attorney general in the early 1960s, said Seigenthaler was "thought to have been directly involved in the Kennedy assassinations of both (President) John (F. Kennedy), and his brother, Bobby."

Although Wikipedia founder Jimmy Wales has said that erroneous submissions are usually corrected within minutes, the Seigenthaler "biography" stayed on the site for 132 days before it was corrected. In addition, the "scurrilous text" appeared on search engines Reference.com and Answers.com, Seigenthaler said in a Nov. 29 editorial in USA Today.

"I have no idea whose sick mind conceived the false, malicious 'biography' that appeared under my name for 132 days on Wikipedia, the popular, online, free encyclopedia whose authors are unknown and virtually untraceable," Seigenthaler said.

In acknowledging the incident, Wales said Monday it was an unusual case in which the site's safeguards failed.

"It slipped through the cracks is basically what happened," Wales said.

New articles submitted to the site are first looked over by volunteer editors, who categorize and post the submissions. In this case, only minor changes and a couple of links were added.

"Somehow in the process, this article got overlooked," Wales said.

As a result of the incident, Wikipedia no longer accepts new submissions from anonymous contributors, Wales said. A person now has to register with the site before contributing an article. By doing this, site managers can at least determine whether a person associated with a specific user ID is submitting false information, and prevent articles from being submitted by that registrant.

The new procedure, however, would not help in identifying the person, since contributors are not required to give their name or other identifying information. The assumption is that people who register first will want to maintain credibility.

"It's a reputation mechanism as opposed to a gatekeeper," Wales said. "We (at Wikipedia) talk about accountability over gatekeeping."

In a separate incident, Adam Curry, credited with developing the technology that helped launch podcasting, acknowledged changing Wikipedia's history on podcasting to remove the name of Kevin Marks, who was also credited with helping to launch the new form of Internet broadcasting.

The former MTV VJ apologized on his blog for removing references to Marks, a software engineer who contributed podcasting technologies.

"I apologize to Kevin Marks for my history of removing this fact on WikiPedia," Curry said. "I really believed this was untrue."

Wales acknowledged that Wikipedia has its flaws, but stood by the online encyclopedia's open approach to developing content.

"We've always said that Wikipedia is a work in progress, and it's our goal to be as good as (Encyclopedia) Britannica across the board," Wales said.

For now, however, there are some topics Wikipedia covers very well, such as technology, while others are weaker, such as content on the humanities, Wales said. Nevertheless, he insists that the quality of information is steadily improving, and "we expect that process to continue in the future."