As you might already know, a great way to increase your AdSense earnings is to place multiple ad units on webpages that are rich with content. Here's a way to maximize your revenue with multiple ad units: Make sure the ad unit with the highest CTR is the first ad unit in the HTML code of your page.
Currently, the first ad unit on a page always shows the top ads that win the ad auction. Also, if there aren't enough ads in our ad inventory to fill all of the ad units on a page, the first ad unit on the page will display ads first. This is why I recommend using custom channels to determine which of your ad units has the highest CTR, and then placing that ad unit first in the HTML code.
For the purposes of this post, the first ad unit on the page is defined as the first instance of the ad code within the HTML of the page. Keep in mind that the first ad unit in the source code is not always the first ad unit that your users will see when the page finishes loading in their browser. For example, if you use DIV tags, our system may recognize an ad unit which users see at the bottom of the page as the first ad unit. Now that you know how to make the most out of multiple ad units, try this tip and watch your earnings grow.