There are different formats known as standard banner size.
The standards evolved from guidelines several market leaders
worked out in early days. Of course, everybody is free to define
their own formats but we recommend you design your banners
in standard formats to correspond with most advertisers. You
may want to take the graphics (right click and "save to disk")
we created to see what they look like in your website design.
The size of ad units is defined in pixel - width x height. Set the
values of your image to the respective format when you start
designing your banner.
We list the most popular formats. You may identify other formats
surfing the web. Have a look at your favorite websites to get
some impressions what banner size they are using.