Banners are particularly important because they are at the heart of Internet advertising. Their main purpose is to produce clearly advertising messages. Their messages are directed to the users of a particular web site.
Most clearly formulated, banners represent the ad slots on a site. They can represent static pictures or may be animated. What will you choose entirely depends on what the specific purpose of the banners is. It's important what exactly they're advertising and what kind of audience they're targeting.
Based on the preferred technology for building banners, they can be divided into three main types. There are .jpg - banners that represent static photos. There are .gif - banners, also called animated banners. The third type is .sfw - banners, also known as flash animated banners. There is a very thin border between the last two species. The difference is in the created animation and in the size of the file. If you choose animated banners for your site, you will need to find out which of the two types is more suitable.
Banners can generally be in any sizes, everything depends on the situation and the place where they need to be placed. However, it always aims to maximize standardization. For this reason, the Bulgarian Web Association has adopted several sizes as standards.