An ad format is a web page branding with a single HTML panel, or multi HTML panels - left, right and, optionally, top. Each panel may contain different target URL.
Branding: width and height depend on a web page layout. Make sure that the banner content (top, left and right sides) is aligned as close to the website as possible, so it is visible on most screen resolutions. The website background color should be considered on the borders of the banner-to-website background transition.
Branding panels are HTML files.