Here is a secret weapon that would increase your ad relevancy.

A lot of times, our website HTML source code has a lot of formatting code, some code for the sidebar, some other advertising code, javascripts, and other code snippets aside from our main content.

What we normally want is to have ads that are relevant to the content of our site. Google's spiders read your whole site (all the code in it), and use that as a basis for the ads to be presented. However, if you have a lot of non-content codes such as the ones I mentioned above, it often affects the relevancy of the google ads presented.

The best way to remedy this is to use what we call "section targetting". With section targetting, you specify a starting tag, and an ending tag that emphasizes the enclosed content to the google spider.
The HTML tags to emphasize a page section take the following format:
<!-- google_ad_section_start -->

<!-- google_ad_section_end -->

With these tags added to your HTML code, your final code may look like the following:
<html><head><title>Section targeting</title></head>
<body>
[....some other code here such as your sidebar code or some header graphics..]
<!-- google_ad_section_start -->


This is the text of your web page. Most of your content resides here.
<!-- google_ad_section_end -->

[...some other code here such as blogroll or footer code, or other non-content code...]
</body>
</html>

What happens is that google will give more importance to the "targeted" section which results to a better and more relevant adsense ads.