Use standard banner ad sizes

Banner ad size standards are set by the Internet Advertising Bureau and by the publishers of popular websites such as Yahoo. While there are many different sizes used today, there is a set of standard banner ad sizes (http://www.theoremcreations.com/ppc/bannersizes.php). Using these banner ad sizes will give your ads portability, which means you will be able to use them across a wide range of websites. If you are only going to create one banner ad, your best bet is to create a 468 pixel by 60 pixel banner ad. This has remained the most widely used banner ad size.