You will sometimes see it on your own site as an assurance that it is active in the network. Extra impressions are allowed for this. When you join, you will receive 500 bonus impressions to get your web site noticed straight away. From time to time, more bonus impressions will be awarded, for example at particular times of the school year, such as January and September. Your banner should be 468x60 pixels and up to a generous 15k in size.
Animated banners are fine.
A web search will show you many sites where you can design a banner, online, for free. Here is an example of one of our banners. Eventually, there will be a small bar below the banner telling people where to join the banner exchange network, thus making the network even more effective. How to join Click on 'Join' in the box below, then follow the instructions. You will then receive an email with a password and further instructions.