- Allow all ad sizes to show on all placements
- Create new display ads that will work well with the ad sizes that are not working properly
- Continue to redesign the ad using the Ad gallery until the content appears properly for all desired ad sizes
- Target placements that only accept ads in the sizes that display the content properly
Explanation: When you create your ad, you’ll have the option to select the ad sizes we provide for your ad. In some cases, these ad sizes may not work well with the size of the image you provided, so be sure to check that your image displays properly in the ad size you want by using the preview. Don’t use a size if the images or content don’t display properly.
Read more here: https://support.google.com/adwords/answer/2549129?hl=en