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 will get the standard banner size idea for online advertising from below size chart. The size of ad units is defined in pixel - width x height. Set the values of your banner size to the respective format or create your own size 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.