One the factors that affect click through rates on AdSense is the complexity and simplicity of the webpage design.
Webpages that have a simple, clean look, tend to attract more clicks, than sites that are busy with lots of clutter.
Every element on a webpage will compete for attention from the visitor's eyes. The more elements on a webpage, the fewer clicks you'll get on your AdSense placements.
But don't go removing everything from your website in a zealous endeavor to boost your AdSense CTR. What you need to do instead, is to make sure the elements you have on your website are clearly identified as to what their purpose is.
That is, if you have a place on your webpage for reciprocal links, or a blogroll, then make sure they are labeled as such, and make sure this area has plenty of empty space around it so that it can be clearly recognized at a glance.
Remember, statistics show that about half of your visitors will stay at your website for only 5 seconds or less. What can you do to reduce that percentage? A simple clean website design will help them find the content they're looking for.
Here's a helpful tip...
Try to put yourself in the mind of someone who's visiting your website for the first time, and who has no idea what this website is about. When the website opens up on your web browser, on what area of the page do your eyes want to come to rest?
If your eyes tend to wander around, looking at all the elements, graphics, blinking buttons, and flash animation, then you're basically not looking at anything at all!
As a rule, your eyes should find a comfortable place on the webpage to rest on. Hopefully, that place is your main content. From that point, you surround it with other important elements like navigation links, a site logo, and ads.