On this page I'll explain the basics of using banners to market your website. File size is important. Smaller files load faster , and that's always better. You can shrink a banner's file size without changing its appearance by using one of the many utilities made for that purpose. Adobe's Image Ready , Macromedia's Fireworks and JASC Software's PaintShopPro all have filters that reduce file size while maintaining image quality.
Static banners have a smaller file size than animated banners.
That makes them load faster and that can often be more important than a higher clickthough ratio. Static banners are mostly for other sites to host. Other people don't want to host a huge, slow loading animated banner because it costs bandwidth and slows their page. To attract the eye . Two layers give you twice the space.