How Does Google Know What Ads Will Interest My Audience?

Google's AdSense engine, as with everything Google, is rather sophisticated. Rather than simply serving up random ads from its advertiser base, Google works hard to make sure the ads your visitors see are likely to pique their interest.

From the day you start offering ads, the AdSense robot visits on a regular basis, reading through your pages with ads. The robot takes a look at the words you use, the frequency with which you use them, even some of your page structure and formatting (for example, bigger fonts usually signify something important). Then Google uses all this info to figure out which ads your readers will warm to.

Even better, Google takes the language of your site and the location of your visitors into account, serving up language- specific, location-targeted ads for maximum impact. So a visitor from France (or a person browsing the Internet from a Frenchified computer) may see AdWords in French (shown here) or from French companies, while your U.S. visitors see theirs in English, Germans in German, and so forth. (See What Are Google AdWords for an excellent how-to of that service.)
Bottom line: Google may know more about your audience than you do. Use AdSense to work that knowledge to your advantage.

The beauty of AdSense, however, is that it's free—absolutely gratis—to join and run, so you may as well give it a whirl. And the program automatically tailors itself to your site over time, supplying more relevant ads as it gets to know you better or as you change your content. It can take a few months before Google hits the sweet spot with ads that your readers love, but the only thing you have to do is set it up and watch it go to work. (Bear in mind, however, that participating in AdSense doesn't have any effect on your site's rank in Google search results.)

Warning: Don't try to game AdSense. It probably won't surprise you a whit to learn that people have set up sites primarily to showcase ads and draw lots of clicks (and make buckets of money). When Google finds out about these sites (and it often does) it blocks the ads immediately. But dirty play makes the whole system weaker, and it harms not only Google but the people who pay for clicks, too. Don't be part of that damage.