Microsoft's newest browser may block ads

The program also covers other footprints, including temporary Internet files and cookies, the small data files that Web sites put on visitors' computers to track their activities.

Both Internet Explorer 7, Microsoft's current browser, and Mozilla's recently released Firefox 3, already allow users to block cookies. The top two browsers also let users delete private information such as temporary files and browsing history after the fact. But they can't turn off that collection entirely.

The beta also introduces an additional InPrivateBlocking mode, which can block third-party content from appearing on Web sites. For example, a news site might carry stock quotes from one company and weather information from another. Companies that provide such content may also be collecting and sharing information about what people do online. But users who turn on InPrivateBlocking won't see that content or be exposed to such data collection without their consent.

InPrivateBlocking can also keep some types of ads from appearing--including those served up by Microsoft's own advertising platform, whose success is considered critical to the software maker's future.

JJ Richards, a general manager in Microsoft's advertising division, responded in a statement that consumers understand that they get free content and services in exchange for advertising, but want "transparency, trust and control with respect to the sites they visit."

"If IE8 helps heighten awareness of this value exchange, that's a step in the right direction," he said.

Users surfing with InPrivateBlocking turned on can review a list of which companies are trying to display or collect data. Users also can click a link to read more and decide case by case whether to permit certain ones to go ahead.

"Today as a user, we have no visibility or control over how that information is shared and recorded," said James Pratt, a product manager for IE8. "I wouldn't put Microsoft as being the arbiter of what should and shouldn't be tracked."

InPrivateBlocking isn't purely an ad-blocker by design, but publishers are still worried, said Mike Zaneis, vice president of public policy for the Internet Advertising Bureau, which represents Web publishers.