I've uploaded an ad designed by someone who knows the exact specs for square ads on my website. However, when I uploaded this ad to AdPlugg, it won't appear and instead shows up wth the icon for a broken image. This is an updated image for the ad and the previous image worked just fine, just had a typo.
The ad is 310 pixels by 255 pixels and is in JPEG format. I'm not sure what else could be going on with it.