Digital Media

This story has been updated. See below for details.

Keynote Systems, a company that measures Web site performance, created some confusion on Friday by acknowledging that it released easily misunderstood data on how Web news services fared following the death of Michael Jackson.

Keynote follows a multitude of Web sites and monitors their performance with the help of 3,000 servers in 59 countries. On Thursday, the company said the online units of major news services became nearly inaccessible for long periods of time, as people rushed online to learn about Jackson's condition.

However, site accessibility wasn't necessarily as bad as Keynote initially reported. There is no question that many media sites were under a strain starting at about 2:40 p.m. PDT, but to what extent and exactly which Web sites suffered the most is hard to determine, Keynote said.

Keynote initially said ABCNews.com was nearly impossible to log on to for nearly two hours. Dan Berkowitz, a Keynote spokesman, said Friday that in truth the site delivered pages to visitors at close to normal speed during the hour-long traffic spike following Jackson's death. A representative for Disney, which owns ABC, said the company saw "no dips in performance" as a result of the traffic glut.

"We apologize for this," Berkowitz said. "This has never happened before and it won't ever happen again."

The reason for the confusion, according to Berkowitz, had to do with the way Keynote follows the serving of ads. Apparently, some third-party ad vendors had trouble loading ads to the millions of pages being delivered. Depending on how the Web pages on news sites are constructed, this could have contributed to a slowdown, Berkowitz said.

In other cases, news stories would have loaded just fine, he said.

In Google's situation, the search engine acknowledged that some users couldn't access Google News for about 20 minutes after reports began circulating that Jackson had collapsed. It turns out Google's systems misinterpreted the traffic spike as an attack.

Update, June 29 at 11:15 a.m. PDT: Changes reflect additional information about Keynote's data collection methods.