This is no surprise, and I believe I’ve written about it before. (With almost 1K posts, it’s hard to remember.) But here’s the deal: Google is tightening its algorithm to exclude sites without enough content above the fold. 
In a January 19 post to their Official Webmaster Central Blog, Google writes:
“In our ongoing effort to help you find more high-quality websites in search results, today we’re launching an algorithmic change that looks at the layout of a webpage and the amount of content you see on the page once you click on a result.”
It seems that people were complaining that when they clicked on a result, they had difficulty finding the content on some pages in the index. Google wants the best client experience (search experience) ever, and so…
If you have a WordPress or other platform theme that places a strip of ads above your content so that you can’t see much when people click your link, or you have one of those very tall headers, think about changing your game. Google is continually tightening things down and this is one place where they’re adamant about rubbing out “carnival” (my word) sites that show so many ads that it looks like crap.
On the other hand, Google recognizes the need to monetize, so they’re not going to penalize you for advertising, as long as you’re doing it in the right place — below the fold. Or, maybe in a delayed pop-up or exit pop. Yes, I know they can be blocked, but there are the non-blockable type, too.
So, as the old saw says, “Everything in moderation.” Google doesn’t want to see too many ads, even if they are below the fold. Pick one or two products that sell well and use those. Or, there are WordPress plugins that allow you to have different sidebars on each page, so you may want to try that.
As with everything in marketing, it’s all about testing and tracking. See what works best for you
