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.
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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