It's one of those smart internet ideas that's been surprisingly slow to catch on: behavioral targeting. It's where the advertiser places the message in the path of the user, based on the user's past behavior. That's opposed to traditional targeting, where the ad is placed against content the advertiser assumes the user will be interested in.

But at last behavioral targeting is showing real acceptance among advertisers. A new study reports that nearly one in four online advertisers, 23 percent, plan to use behavior targeting in 2007, up from 14 percent this past year.

"Advertisers are starting to embrace behavioral targeting," says Emily Riley, advertising and marketing analyst at JupiterResearch, which conducted the study. "For some it is just another tool in the tool box. But for others, particularly advertisers with long purchase cycles, it can really be an important tool."

That may well be because of the results it delivers. Jupiter's researchers found that 88 percent of agencies that used behavioral targeting in the last 12 months were somewhat to very satisfied with the effectiveness of the campaigns. That's compared to 56 percent of agencies that relied on traditional targeting methods.

Behavioral targeting, which relies on sophisticated tracking technology, is still only offered by a handful of companies. Among those offering the service are Tacoda Systems and Revenue Science. There are also companies, such as Yahoo, that offer aspects of the service across their own properties.

In effect, there are two basic types of behavioral targeting, known as extended-content targeting and purchase-intent targeting.

Extended content targets users who have shown an interest in a subject, say flyfishing or golf, by placing the advertiser's message, say for a new, light-weight reel or a putter, when the user has moved on to new content, even unrelated content, as Riley explains.

So, for example, through the behavior software we know that someone has read at least three golf articles in the last month. The putter-maker can then arrange to place his or her ad against whatever new content our golf fan pulls up, whether it be about golf or investment banking or the weather, for that matter.

The advantages are pretty obvious. The advertiser is reaching consumers known to be interested as opposed to consumers who he has reason to think may be interested, which should produce higher results at less cost. Extended content is generally used for branding.

The other form of behavioral targeting, purchase-intent targeting, allows advertisers to direct their messages at users who are about to make a purchase. For instance, someone that has been researching convertibles on an auto site could be targeted with relevant advertising when they are elsewhere on the internet.

"Purchase-intent targeting pinpoints someone that is about to buy something, not just someone that is interested in a particular subject matter. So for advertisers that is like magic," says Riley.

Jupiter's study found that in 2007 behavioral targeting will close in on content targeting and demographic targeting, the two traditional targeting methods. Content targeting will be used by 25 percent of advertisers next year, while 28 percent will target by demographic. That’s not far ahead of the 23 percent of advertisers that intend to use behavioral targeting.

Riley credits the change to the increasing sophistication of the tracking technologies and advertisers' increasing faith in their reliability. Behavioral targeting is expected to see its biggest gains among advertisers of products with long purchase cycles, such as cars, supplanting traditional content targeting in the next 12 months.

Meanwhile, in online ratings for the week ended June 18, Microsoft was the top parent company, followed by Yahoo, Time Warner, Google and News Corp., according to Nielsen//NetRatings. Top brands were Yahoo, Google, Microsoft, MSN and AOL.

GUS Plc once again retained the top spot among advertisers, delivering 5.27 million impressions to No. 2 Vonage’s 3.74 million. Yahoo served up the most ads, 18.96 million, followed by MySpace at 7.37 million.

Sessions per person averaged 16, and domains visited per person were at 37, with the average PC time per person at 16 hours, 5 minutes and 5 seconds for the week.