For campaigns that are targeting mobiles and tablets it is recommended to upload the following creative sized:
* 320x50, 300x50 (smartphone banner, most common)
* 320x480, 480x320 (smartphone interstitial)
* 300x250 (mobile interstitial, tablet in-app, mobile web)
* 728x90* (tablet only)
* 1024x768*, 768x1024 (tablet interstitial)