Images: Microsoft AdCenter stages

AdCenter is Microsoft's own homegrown ad-delivery system. It replaced Yahoo technology that the company had been using to serve ads up to its MSN site. Potential advertisers can register for an account online, then complete a four-step process to getting their promos delivered. Step one, shown here, is the Settings page, where people outline their campaign.

Advertisers can submit desired keywords. The tool is designed to help them target their promo at a particular market, depending on age, gender or lifestyle, for example.

This page gives marketers estimates of how much a campaign might cost, depending on keywords and key phrases.