Just killing time surfing the Web? Now that endeavor can earn you some spending cash.

A Palo Alto start-up, AllAdvantage.com, says it will pay Web lovers for each hour they spend on the Net.

The catch?

Participants have to download a viewbar that sits across the bottom of their computer screen, flashing ads and other information from AllAdvantage.com. The viewbar can be turned off, but Web surfers only get paid -- 50 cents per hour, up to $20 per month -- when the viewbar is visible.

"It's a share-the-wealth kind of thing," said Jim Jorgensen, AllAdvantage.com's chief executive.

There are other rewards-based companies online. For example, Cybergold of Berkeley pays its 1.5 million subscribers for visiting advertisers' Web sites. And MyPoints of San Francisco offers its 2 million subscribers points that can be redeemed for goods and services when they click on ads.

AllAdvantage will pay people simply for allowing the viewbar to occupy screen space. Consumers don't have to click onto ads to get their check in the mail.

About 60,000 people signed up for free registration by the end of last week, said Jorgensen, who co-founded Discovery Zone indoor playgrounds for children.

But his business is drawing some skeptics. Michele Slack, an analyst with Jupiter Communications, wonders whether advertisers are going to want to have their ads flash on AllAdvantage viewbars.

"You really need to think about the quality of audience that they are getting," Slack said. "I question if they will get a demographic that is valuable to the majority of advertisers. Is Mercedes going to sign up? I don't think so."