Have a look at the Google heat map which shows that how a person scans a web page from top to bottom.
Thus if you are a prospective advertiser, you must make sure that your advt appears in the top left portion and one will have a higher click through rate provided one can make the ad appear in such a manner that the buyer need not scroll down the page.
Thus using a correct strategy of placing ads, one can have a high click through rate which means that more people land on your landing page and will get converted and thus you get a higher business growth by virtue of increased sales.
