Nielsen says it's not what sites you visit but how long you stay

Nielsen/NetRatings to change Web site ranking to focus on time spent rather than page views

In a move that will definitely favor viral video sites over search sites, Nielsen/NetRatings is going to start ranking Web sites by how long people spend on them instead of by how many page views they get.

"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," according to the Associated Press. "Currently, sites and advertisers often use page views, a figure that reflects the number of Web pages a visitor pulls from a site."

However, with the advent of Ajax, software that allows sites to update data automatically without having to pull new Web pages, the measurement isn't as accurate as it once was.