In a nod to the success of emerging Web 2.0 technologies like AJAX and streaming media, one of the country's largest Internet benchmarking companies will no longer use page views as its primary metric for comparing sites.

Nielsen/NetRatings will announce Tuesday that it will immediately begin using total time spent by users of a site as its primary measurement metric.

Scott Ross, director of product marketing at Nielsen/NetRatings, said the change was prompted by a continuing increase in the use of AJAX, or Asynchronous JavaScript and XML, which allows a Web site to refresh content without reloading an entire page, and to the growing use of audio and video streaming.

"It is not that page views are irrelevant now, but they are a less accurate gauge of total site traffic and engagement," Ross said. "Total minutes is the most accurate gauge to compare between two sites. If [Web] 1.0 is full page refreshes for content, Web 2.0 is, 'How do I minimize page views and deliver content more seamlessly?'"

For example, he said, MySpace may have 10 to 11 times more page views than YouTube, but myspace.com users spend only three times more minutes on the site, Ross added. Therefore, measuring total time spent on a site will make it easier for advertisers to mold their ads to how users are actually accessing content, he said.

"On YouTube there will be more ads flowing in based on duration (on videos)," he said. "The more time I spend on YouTube ... [advertisers] will figure out a way to monetize that."

Nielsen/NetRatings will still report page views as a secondary metric, and it will continue to reevaluate its primary metric as technology continues to evolve, Ross added. "For the foreseeable future, we will champion minutes if you are comparing two sites. Going forward, we'll see what that equates to in terms of true advertising opportunity," he said.

The change will affect the rankings of some companies immediately, Ross said.

For example, AOL will get a boost because the time spent on its popular instant messaging application now will be the primary measurement in its Web ranking.

And while Yahoo and MSN likely would maintain their current rankings, Google will probably ratchet down on the list because while users visit the site often, they don't usually spend much time there, according to Ross.