Not always the best choice for photo-realistic images. Joint Photographic Experts Group. A common file format for photo-realistic images. This graph shows CPCs for 4 common CPMs. An expanded table is also available.
Some people feel that animation in a banner helps increase the click-through ratio.
Personally, we at Webmaster Yellow Pages are not convinced. We have done tests that show an animated banner can have a lower CTR than a visually similar non-animated banner. Animation will make your banner bigger in bytes and, therefore, make it slower to download. Since a good portion of the world still surfs at 28.8 or slower, bandwidth is an issue and they will never get a chance to see your slow-loading animated banner because they've clicked off to some other page before your banner even appears. Designs by Mark - Almost a complete resource for Banners and Ads.