What is Side Ad?
Side ads refer to the ads that appear on the right-hand side of the search results page in Google's desktop search.
However, in 2016, Google made a major change to its desktop search results by removing ads from the right side of the page and placing them only at the top and bottom.
This change also introduced the possibility of an additional fourth ad appearing above the search results for highly commercial queries. The change had been in testing since 2010 and was gradually rolled out to all desktop searches in all languages worldwide.
The only exceptions to the removal of right-side ads were Product Listing Ad (PLA) boxes and ads in the Knowledge Panel.
This change made the desktop and mobile search results more similar, as mobile typically shows only two or three ads at the top of the search results.
The reason behind removing side ads
The reason behind Google's decision to remove ads from the right side of its desktop search results and place them only at the top and bottom was likely to improve the user experience and increase ad performance.
By reducing the number of ads on the page, Google may have hoped to reduce ad blindness and improve the relevance and visibility of the remaining ads.
Additionally, by introducing the possibility of an additional fourth ad above the search results for highly commercial queries, Google may have hoped to increase ad revenue for these queries.
Overall, this change was likely a strategic move by Google to balance the needs of users and advertisers and improve the effectiveness of its advertising platform.