Clock Watchers

This development (which is reported in today's Wall Street Journal) bodes well for Pandora, whose users spend many hours on the site each month.

Nielsen/NetRatings, a leading online-measurement service, will scrap rankings based on the industry yardstick of page views and begin tracking how long visitors spend on Web sites.

The move, 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.