Buying an ad in a print publication won't include statistics tracking the number of people who actually saw the ad or even opened the page featuring your ad. You can't rotate ads based on the number of times someone opens the same page -- i.e., the first time someone opens the page, ad number one appears while ad number two appears the next time. You can't filter your ad only to female readers who earn over $50,000 a year and work in the financial services business. Of the people who look at your ad, you cannot even record the time spent looking at it. The only piece of hard data you have is the total number of printed copies. Everything else is speculation. 

Not so in the world of online advertising. Portals, online magazines, and almost every type of Web site in existence -- down to your kid brother's skateboard hobby site -- features an ad of some sort, even if it's just a little affiliate link program. Large operation that serve out millions of impressions must have a way to keep track of them and to meet the advertisers' demands.

The dominant methods of paying for ad space online is based on either the number of views or the number of actual clickthroughs. Additionally, advertisers may want to periodically rotate ads or have them appear only under certain circumstances, such as when a previous visitor with specific demographics makes a return visit. A category of technology called ad management software may be of some use here.

Working for a small-town paper, I did ad management when I typeset an ad on an ancient Merganthaler phototypesetting machine, laid it out on a light board, typed out a form using a manual Smith-Corona that weighed about a hundred pounds, paper-clipped everything together, and filed it in a drawer. There was no ad management software; there were no computers; and the old "hot type" Linotype machine, which produced lead type, had just been replaced by the Merganthaler but was still in general use. But I digress.

Ad management software lets you serve out ads to meet very specific criteria. You can rotate ads on a schedule and target ads to certain demographics. In other words, the client who wants an ad delivered only to viewers who wear purple socks on Tuesdays, speak Czech as a second language, live in the Northeast, own their own home, and work in the manufacturing industry, can do so.

When selecting an ad management software package, keep the following features in mind:

1. The ability to match ads to specific content. This would, for example, let you run an ad from a car company next to an article on the Indy 500. 2. Tracking. Of course, you'll need to deliver detailed metrics to your customers showing impression rates, clickthrough rates, and other metrics. 3. Rotation. Advertisers will want to rotate different ads in the same space. 4. Spacing impressions. If an advertiser buys a given number of impressions over a period of time, your software should be able to adjust the delivery schedule so that they are spread out evenly over time.

Plenty of ad management software packages are available, including some ASPs and some freeware, but one of the better-known offerings is AdManager from Engage (http://www.engage.com), which delivers all of the above features.