Nielsen//NetRatings, a leading online measurement firm, recently announced that will start ranking websites based on time spent on sites rather than the industry standard of page views.

The decision comes as online video websites, such as Google Video or YouTube, and new technologies such as AJAX, make page views less significant.

”Ajax, or AJAX (Asynchronous JavaScript and XML), is a web development technique used for creating interactive web applications. The intent is to make web pages feel more responsive by exchanging small amounts of data with the server behind the scenes, so that the entire web page does not have to be reloaded each time the user requests a change. This is intended to increase the web page’s interactivity, speed, functionality, and usability.” [Wikipedia]

This change might change the way advertisers, who currently use impressions as a figure that reflects the number of web pages per visitor, determine the value of a specific website.

By the moment, though, Nielsen//NetRatings will continue to provide page views figures, as well as “average number of sessions per visitors” and “average time spent” for each website, but it will start reporting total time spent and sessions for all visitors to give advertisers, investors and analysts a broader picture of what websites are more popular.

“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.

comScore Media Metrix, Nielsen//NetRatings major rival, has also addressed the increasing use of AJAX with the development of site “visits” (number of times a visitor returns to a website with a break of at least a half-hour).