If you’re familiar with AdSense you’ll be aware that you can have 3 ad units and 1 link unit per page. Many webmasters make the mistake of using the full allocation thinking the more ads there are the more likely a visitor is going to click them and therefore the more money they will make.
This doesn’t work in my experience (and the experience of other webmasters I have spoken too) and here is the reason why.
What ever you web page subject there will be AdSense ads of varying value. Google will always display the most valuable ads because they want like you to make the most money. Now if you have all three ad units in play on the page not only will you have the most valuable ads but also you will have the ads from companies who paid considerably less. Obviously if people click on one of these less paying ads you may only be getting a few cents.
Therefore my advice to you is to have a maximum of one ad unit and one link unit per page. That way when you get clicks from your visitors they are more likely to be of a higher value.
Having fewer ads on your pages also has the benefit of making your page look more professional. There’s nothing worse than coming to a page which is swamped with AdSense ads it’ll have the majority of your visitors hitting the back button long before they read the ads let alone click on them.
If you don’t believe me choose a page with reasonable traffic and test it for a couple of weeks. If you’re not earning as much as before you can always change it back. I’m willing to bet though after you see the improved ‘Click Through Rate’ (CTR), page ‘Effective CPM’ (eCPM), and ultimately earnings for the page you’ll be changing the rest of your site to the same format.