One of the most common mistakes in banner design is over-inclusiveness. Often, advertisers will attempt to jam pack as much information as possible into a single ad in a misguided attempt to get the most out of each impression. Prima facie, this may appear to be a good tactic, but attempts to include too much information often end up conveying no meaningful information at all. With any banner ad, you have only a moment to grab the attention of your viewer and make an impression. Additionally, banner ads offer extremely limited real estate. Packing information in tiny, unreadable text will neither effectively relay that information nor make a lasting impression. Including too many images or overly complex graphics will have the same negative effect.

Due to limited space and the small window of opportunity to catch the viewer, your goal should be to make a lasting impression. Eye-catching backgrounds should be paired with short taglines that explain your product or value proposition as effectively as possible. There can only be one call-to-action, and it should be simple, declarative, and bold.