NEW YORK — At Yahoo's finance site, stock quotes update automatically and continually, the numbers flashing green and red as prices rise and fall. Wall Street investors can easily leave a single Web page up all day.

Ajax — the software trick used on the page, Yahoo Inc.'s e-mail service and elsewhere — is enabling flashier, more convenient sites. It's also contributing to Yahoo's decline in page views, a yardstick long used for bragging rights and advertising sales.

"These technologies have outgrown the metrics," said Peter Daboll, Yahoo's chief of insights and the former chief executive of comScore Media Metrix, the measurement company that declared Yahoo second to the online hangout MySpace in page views. "It's really important as an industry to come back down to earth and off this chest-thumping about who's biggest."

More important than "truckloads of page views," Daboll said, are visitors' loyalty and their willingness to respond to ads — qualities harder to measure. If a page updates on its own without reloading in its entirety, people may be sticking around longer than the measurements suggest.

Experts say the stubborn attachment to page views also may be keeping some sites from improving their usability.

Jakob Nielsen, a Web design expert with Nielsen Norman Group, notes that many news sites force visitors to click multiple times to read longer stories in sections, even though he would much prefer scrolling down a long story and avoiding interruptions.

"Because you are measuring the wrong things, you are driving your project in the wrong direction," Nielsen said. "You are not maximizing what causes value. You are maximizing the things a computer can count easily."

Many Web sites and advertisers, however, continue to value page views, and MySpace officials say their users continue to return frequently even as the site requires full page reloads for just about everything.

"Over time, page views have been a pretty accurate measure of a site's popularity," said Michael Barrett, chief revenue officer for Fox Interactive Media, the News Corp. unit that oversees MySpace. "A page view doesn't necessarily equal an ad opportunity, but (is) an important barometer."

The leading measurement companies aren't about to abandon page views, either, even as they develop supplemental measurements for gauging consumer interaction and loyalty.

"People kind of cling to it, even if they know it's flawed," said Gregory Dale, chief technology officer of comScore. "They want to see this familiar metric."

According to comScore, MySpace managed in just three years to edge out Yahoo as the busiest Web site in the United States by page views. In December, MySpace had 41 billion page views compared with Yahoo's 36 billion, down 2 percent from a year earlier.

Yet Yahoo remains arguably the Internet's leading brand — both in terms of the number of unique monthly visitors and the average time spent, according to comScore.

Over the past year, Yahoo's monthly audience grew 3 percent. To throw even more confusion into the mix, rival Nielsen/NetRatings has Yahoo leading in page views as well.

Even before Ajax, techniques for measuring Web audience have come into question.

Through much of the 1990s, Web sites touted "hits" — the number of elements pulled from a server.

But that rewarded sites heavy with graphics and photos, even though too many can be distracting, especially with dial-up connections the norm at the time, design expert Nielsen said.

Companies like Nielsen/Net-Ratings — no relation to the consultant or his firm — started refining which hits should count, said Dave Osborn, a director at Nielsen/NetRatings. All elements in a single page are counted as one, and thus "page view" was born.

It became a good gauge for advertising potential because it's roughly proportional to the number of ad impressions — whether a site typically displays one, two or more on a single page. Advertisers look to it in deciding where to place ads.

Marketers also turn to unique audience — the number of visitors to a site in a given month, whether that person visits once for 10 seconds or several times.

The measurement is reflective of a site's reach as advertisers like to know they aren't displaying ads to the same people over and over, even if the site draws significant page views.

Together, the two measures have served Web sites and advertisers adequately, despite frequent inconsistencies between comScore, Nielsen/NetRatings and often a site's own logs.

Adjustments were made along the way to account for new techniques such as pop-up ads, which appear to a computer like a regular page view and thus could artificially inflate a site's count.

But now comes Ajax, "the first that has changed the model of page views from an impression measurement perspective," said Sheryl Draizen, senior vice president with the trade group Interactive Advertising Bureau.

Her organization has convened a working group to set industry standards on how ad impressions should be counted in light of Ajax.

Other technologies that could deflate page views include Really Simple Syndication, or RSS, which pulls a news site or blog's new entries, allowing a visitor to bypass a site's home page — and ads — for the item of interest. Likewise, someone can watch a three-minute video clip without needing to retrieve a new page.

In such cases, visitors may view fewer pages, but they are more engaged and thus more likely to pay attention to any advertising, said Steve Rubel, senior vice president with the public-relations firm Edelman Worldwide.

"It's easy to get eyeballs now but it might not be the right eyeballs," Rubel said.

Page views have their roots in traditional media, comparable to a newspaper's circulation or a broadcaster's viewership.

Although measures for those media have had to adapt to developments such as the rise of video recorders, they were seen as the best available.

With the Internet, it became possible to measure not only how many people viewed an ad but what they did with it.

Google Inc., in particular, has been adept at pushing an alternative model of charging only when a visitor clicks on an ad.

Jesse James Garrett, the Adaptive Path LLC president who publicly coined the "Ajax" term two years ago, suggests scrapping page views entirely.

"Page views have been a broken metric for a long time, and the industry has tried to put a good face on that," he said. "Now a new technology has come along to force the industry to deal with the fact that page views are ... not a good way of measuring audience engagement."