One problem you may encounter when using large Adsense ads is an ugly yellow background when a smaller ad is displayed for the set size advertisement. This issue, as shown in the screenshot below, normally affects WordPress websites and this guide shows you how to resolve it.
Surprisingly, the issue is not caused by Adsense. It is caused by the theme itself.
Add the following to your CSS :
ins.adsbygoogle {
background: transparent !important;
}
After web browsers have taken notice to the new piece of CSS code, the yellow background from all ads should disappear. Transparent is used instead of a specific color for ads to blend in with any background color of the theme.
A fill rate below 100% may cause empty spaces in ad spot locations when ads are not displayed.