Retargeting is the process of serving ads to a visitor after they have left the advertiser’s site. This means that the ad agency serving ads on behalf of the company is able to track visitors as they move around to other sites, and push the same ad in front of them again.

This is important because any online seller is only able to capture 2% of first-time visitors.

The other 98% move on to other sites and sellers. Retargeting gives a seller an opportunity to put targeted ads in front of this other 98%.

The way it works is that the ad serving agency puts a cookie into the browser when a visitor first enters the seller’s site.

Now, when the visitor opens up another publisher’s site or blog that is also being served ads by the same ad network, the visitor will see ads from the seller visited previously.

Note that retargeting is smart enough to filter out the 2% of visitors who have already purchased the company’s product. So it only targets (retargets) the other 98% that have shown an interest but not made a purchase yet.

Also, the kind of ad shown to retargeted customers depends on the type of product. For example, a visitor who just left a travel site has to be retargeted immediately because those doing travel research will likely buy a travel product very soon. On the other hand, a luxury item buyer can be given some time and then retargeted, which often works better.

How is this useful to the blogger? Well, for starters, the visitor is known to be interested in the product and company behind the ad being retargeted. This means there is a greater chance for a click-thru and/or conversion than an ordinary visitor. So the blog revenue and conversion ratios from retargeted ads are much higher than ordinary ads.

The second important question is how does a blogger get or activate these retargeted ads? It is mostly just a question of providing enough space for all the major ad networks on your blog. Also make sure to enable both image and text ads for each ad network.

So, if you have a blog and are serving ads using Adsense and a few other networks like Adroll and Kontera, then the retargeting from these networks may already be enabled automatically. They may have an opt-out option for those who do not want to participate in retargeting visitors.

But note that retargeting can boost blog revenues from each network by about 20%, so as a rule very few bloggers will disable retargeting.