Banner ad design is evolving. As with anything else related to the Web, there are few hard-and-fast rules. However, Web advertising "pioneers" have discovered a few best practices, largely through trial and error. So why not benefit from their experience by following these guidelines in your own banner ad design?
The IAB's Web site also includes graphical representations of banner sizes, and the following note: "Use of any of these sizes as a model or standard is strictly voluntary. The IAB and CASIE recognize and intend that the advertising community remain free to experiment with, use, adopt, and propose other sizes and types of banners."
File Size Guidelines So now you know how big to make your banner ad in terms of pixels. But what about in terms of bytes? File size guidelines haven't been standardized by the IAB as have dimension guidelines (see above). So for guidance, look to one of the cardinal rules of Web usability, which is that smaller files mean faster-loading pages, and faster pages mean happier viewers. And happier viewers are more likely to respond positively to an ad, as has been demonstrated in a study of how download times affect click-through rates.
How do you create the coolest, most exciting ad while also conserving bytes? First of all, don't use technology that doesn't serve the purpose of the banner ad campaign. For example, use animated graphics only if they're more effective than static graphics, use graphics only if they're more effective than text, etc. If you do incorporate large, complex files into your ad, make sure they're "optimized" (streamlined to take up the fewest bytes possible). There are numerous free online resources that can help you with this; a guide to some of these is available on the Adbility Web site, under Banner Ad Creation/Image Compression.
Animation Looping Animated graphics - usually in the Graphics Interchange Format specified as GIF89a - contain within a single file a set of images in a specified order. The series can be presented, or can "loop," endlessly - or it can loop just once or a few times and then stop. When you define looping parameters during the design of your animated banner ad, remember that certain choices might increase file size. For example, faster animation requires more bytes, as does continual looping. For this reason, some sites that sell advertising space have restrictions on looping. Make sure you know the policies of your banner's potential home, and be prepared to make some concessions regarding the complexity of animated GIFs.
Rich Media Limitations Before you set out to create a state-of-the-art banner ad by using rich media such as streaming audio or video and Java applets, consider the cost: frustrated and impatient users. Rich media files are by far the largest and will therefore slow your banner ad considerably. They are also the most "elitist," since a significant number of browsers don't handle streaming or Java very well, if at all.
Many sellers of ad space severely restrict the use of rich media in banner ads. So before you put time and money into developing a media-rich banner ad, determine whether it really makes sense given your campaign goals and target market. Do some extensive testing on users that represent your intended audience. Run the ad on older browser versions and slower connections for a true "reality check."