Did you notice that Google recently changed how ads display in the search results pages? Google has eliminated the ads that appeared along the right side of the page — the right rail.
If you rely on your mobile phone for your own searching, you might not have noticed any change, for Google has chosen not to show right-rail ads in the compressed screen of the mobile phone. The layout changes only apply to desktop searches.
If you are a desktop user, you may have noticed the change, but you might have missed it if your searches trigger Google product listings (PLAs), for Google plans to continue displaying them in the right-hand panel. We can also expect to continue seeing ads in the Knowledge Panel area of the search page.
Instead of three ads at the top of the page, before the organic search results, you can expect to see four ads, particularly for commercial queries. Combined with the three ads that appear at the bottom of the page, seven ads will be shown instead of a maximum of 11.
This change is not an unmixed good. Google does not intend to forego any ad revenue opportunities.
The Google rationale behind the change is that this change will align with how users interact with Google. Reading between the lines, this means that they are seeing huge volumes of mobile search traffic that make it harder to retain any logical reason for offering two different formats.
Their testing has shown that right rail ads are less effective than the ads that appear integrated into the top or bottom of the results page. The right-rail ads have simply become ineffective — interesting news to those who have been spending valuable ad dollars for them. It is my conjecture that users know and recognize that they are ads and, hence, avoid them unless they really answer their needs.