tim222 - 10:30 pm on Sep 4, 2007 (gmt 0)

#*$!? How can google, possibly know, whether an ad clicked on my site, resulted in a phone call?

One way they can tell is when an advertiser uses Google Analytics. But obviously not all advertisers use that, and I *think* that Google guesses by using an algorithm (the buzz word for 2007). The algorithm might take into account factors like where the click originates, the relevancy of your content to the advertisement, and/or other things. Anybody who knows for sure (such as Google software engineers) probably had to sign a confidentiality contract.

As for the suggestion of using smaller ad units to try to get higher paying links - that sounds REALLY logical but I am scratching my head over the fact that my 120x600 ads have a higher eCPM than my 120x240 ads. Could it be that the 600's have twice as many ads and are therefore more likely to display something of interest to more people? Could it be an anomaly with my website? Who knows? The thing is, the eCPM for the 600 ads is not double, but it is more like 5 times! Well, all I can do is keep watching and if that's what works, maybe I'll convert all the 240's to 600's.

Likewise, you could do an experiment using channels. Try various size ad units, and identify each with a channel. That way you'll know which format works the best.

Meanwhile, someone else suggested that red links work better than blue. Personally I'm reluctant to try that because red links would make my website look really odd. But the point is, experimenting with color might be worthwhile, too.