You might have come across Ads with a yellow background while surfing the internet; this issue usually occurs when the ad is smaller than the space you defined for it.
What is Google Adsense?
Google AdSense is a program run by Google through which website publishers in the Google Network of content sites serve text, images, video, or interactive media advertisements that are targeted to the site content and audience. These advertisements are administered, sorted, and maintained by Google. They can generate revenue on either a per-click or per-impression basis.
Why is a yellow background color behind your Google AdSense ads?
The yellow background in a Google Adsense Ad display is usually as a result of the ad unit being smaller than the space you defined for it.