As I've written before, Google's Adsense program is for many people bringing about the dream of having a profitable web publication. I have a link on the right of the blog for those who want to try it. I've been particularly impressed with the CPMs this blog earns, which can be as much as $15. The blog has about 1000 pageviews/day (I don't post every day) and doesn't make enough to be a big difference, but a not impossible 20-fold increase could provide a living wage for blogging. Yahoo publisher's blog ads, which some of you are seeing in the RSS feed have been a miserable failure, and will be removed next software upgrade. They are poorly targetted and have earned me, literally, not even a dollar.

Recently however I noticed a way in which the Google targetting engine is too good, from my standpoint. From time to time my web sites or blog will get linked from a very high traffic site. This week the 4th amendment shipping tape was a popular stumble-upon, for example. I've also been featured from time to time in Slashdot, boingboing and various other popular sites.

When this happens, it's not a money maker because the click-throughs and CPMs drop way down. This is not too surprising. The people following a quick link are less likely to be looking for the products Google picks to advertise. However, more recently I saw high traffic bringing down not just the CPM, but even the total dollars! I theorize that Google, seeing poor clickthrough, cycles out the normally lucrative ads to try others. So even the normal visitors, who have not gone away, are seeing more poorly chosen ads. Or it could just be randomness that I'm seeing a pattern in.

Solution: Consider the referer when placing ads. If the clickthrough is poor on a given referer (like slashdot or boingboing) then play with the ads to hunt for better clickthrough. For the more regular referers (which are typically internal, the result of searches and regular readers) stick to the ads that typically perform well with that group.