Ad placement is very important for a web-publisher. Good placement of ads can do wonders. So, how do you do it? Well, Here is a neat app which will help you with your decision. It uses artificial intelligence (atleast, thats what they say) to simulate first five seconds of vision.
All you need to do is to take a snap of your website and upload it on their website. You will be provided with a heat map of the site, this lets you know where people actually see and lets you decide where to place the ads.
Heres the Link