I recently fielded an enquiry from Louisiana (yes, another unlikely state). The caller was looking to improve his search engine ranking, and wanted to know if InsideBlogging owned a blogging network of sites that could point to his. We don’t, and besides, that’s a bit unethical.
It got me thinking, though, about the value of the referral link. Google AdSense has made it possible to earn a little money off your Web traffic, and offers a decent baseline for the kind of revenue you can generate. Yes, there are more sophisticated ad networks (punch-the-monkey et al) and one could seek out advertisers alone, but Google ads are the simplest solution.
For my analysis, I picked my Hall of Technical Documentation Weirdness, because it gets a lot of traffic, has aggressively-positioned Google ads and I’ve got sufficient ad revenue data to work with. Here’s some math:
From June 1, 2004 – December 31, 2004, I had roughly (heh) 143,126 visitors to the Hall. In that time, Google AdSense says I served 2,508,343 pages. That suggests that each visitor viewed, on average, 18 pages. That would normally be particularly high, but given that the Hall is a gallery, with one image per page, that seems reasonable.
In those six months, my Google ads in the Hall netted me $1,626.96 (all amounts in US dollars) on 2,639 clicks, for an appalling click-through rate. I’ve already provided more than enough data to answer my original question. In fact, this entry has become one of those junior high math questions where you’ve got too many data points and you have to distill the correct ones to calculate on.
The ansewr: if somebody sends one visitor to the Hall from another site, they make me, on average, 1.84 cents. To put it another way, to earn $100 on Google ads, someone would have to send me 5434 visitors. Not big money, but at the moment it’s enough to pay for my hosting.
One further observation on visitors, their origins and click-through rates. The vast majority of visitors to the Hall come from direct links on other sites. Visitors to my archived internal pages mostly come from search engines. For example, this page on Michelle Branch’s butt is (understandably) one of my more popular archived pages (I note that I own top spot for the search “Michelle Branch butt“). The search engine visitors are worth much more than the direct link visitors–twice the per-click income and an improved click-through rate.
UPDATE: Boris kindly points out that Google AdSense’s terms of service require me not to disclose my click-through rates. So, I’ve removed them.
DarrenBarefoot.com 
There’s a good chance even what you’ve kept runs afoul of Google’s rather draconian AdSense terms. I received an e-mail from them a few weeks ago noting that even my saying, in effect, “if you like this article, please click on the ads” violates them, and that I should remove such incitements. So I did.
You’ll need to read the terms carefully and see what you’ve agreed to be able to say and not say. I can understand why Google does it: they don’t want anyone reverse-engineering their payment schemes from statistics people post online. However, you need to be clear that when you sign up for AdSense, you are restricting what you can talk about on your website. I know I have, and I’m a little ambivalent—but there are also plenty of other things to talk about.