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Maybe your browser should have a McDonald's-like sign that reads "Over 24 Billion Served." That's the number of ad impressions--ads loaded into Web browsers--generated in just one week. If you feel that a disproportionate percentage of those ads are hitting you square in the face, you're not alone.

This is not a black-and-white issue. Even people who detest Web ads concede that the explosion in Web advertising has financed a no-cost Internet rich in content. And even the most intrusive ads help pay for the Web's free content (including the news and information at PCWorld.com; see this month's Up Front for more about this subject). If every surfer blocked all advertisements all the time, companies might have to charge user fees for their Web services or, worse, they could go out of business.

But the latest generation of online ads don't just sit meekly on a host page, carrying an identifying label that says "Advertising" and hoping to get clicked. Instead, the ads pose stealthily as noncommercial content or bombard our eyeballs with pyrotechnic excess. And Darwinian competition among advertisers has spawned increasingly aggressive forms, formats, and features of ads.

If you want to put an end to the madness on your desktop, you can use ad-blocking software to eliminate most ads that appear in your browser. We tested four applications (see the features comparison chart below) against the most aggressive ad environments, and found that Intermute's $30 AdSubtract Pro was the most effective.