Total files size – must not exceed 100KB for main HTML file and all additional external resources. This constraint not applied for video Ads.
Ads with light colored/white/transparent background must be decorated with 1px black solid border.
For dynamic size ads 100%×250px etc. height must be fixed (250px). Width must filled min 300px - max 970px. To create effect of 100% width (max 970px) need to show elements across the width (must be adaptive). Is forbidden to use only monochromatic or gradient backing.
Follow the link.