A leading online measurement service will scrap rankings based on the longtime industry yardstick of page views and begin tracking how long visitors spend at the sites. The move by Nielsen/NetRatings, expected to be announced Tuesday, comes as online video and new technologies increasingly make page views less meaningful. Although Nielsen already measures average time spent and average number of sessions per visitor for each site, it will start reporting total time spent and sessions for all visitors to give advertisers, investors and analysts a broader picture of what sites are most popular. Currently, sites and advertisers often use page views, a figure that reflects the number of Web pages a visitor pulls from a site. However, Yahoo Inc. and others are increasingly using a software trick called Ajax to improve the user experience. It allows sites to update data automatically and continually, without users needing to pull up new pages. Page views decline as a result. Page views also drop as people spend more time watching online video at sites like Google Inc.'s YouTube. "Based on everything that's going on with the influx of Ajax and streaming, we feel total minutes is the best gauge for site traffic," said Scott Ross, director of product marketing at Nielsen. "We're changing our stance on how the data should be" used. Nielsen will still provide page view figures but won't formally rank them. Ross said page view remains a valid gauge of a site's ad inventory, but time spent is better for capturing the level of engagement users have with a site. Ranking top sites by total minutes instead of page views gives Time Warner Inc.'s AOL a boost, largely because time spent on its popular instant-messaging software now gets counted. AOL ranks first in the United States with 25 billion minutes based on May data, ahead of Yahoo's 20 billion. By page views, AOL would have been sixth. Google, meanwhile, drops to fifth in time spent, primarily because its search engine is focused on giving visitors quick answers and links for going elsewhere. By page views, Google ranks third. In both page views and time spent, Yahoo is ahead of News Corp.'s MySpace and other Fox Interactive Media sites, according to the Nielsen measures. Yahoo has more than twice the time spent as Fox, but has less than a 10 percent edge in page views. That is because MySpace requires users to pull up a new page anytime they make a change or view a new profile, while Yahoo increasingly uses Ajax to continually pull new data, even if a user stays on the same page all day. Nielsen's rival, comScore Media Metrix, also has addressed the rise of Ajax with the development of site "visits" - defined as the number of times a person returns to a site with a break of at least a half-hour.