Many websites have banner images that are displayed along the top of their site when you first land on it. These banners may rotate or they may be static. Some companies use these banners to have images of their business, staff members or customer testimonials, other companies use these as a way of updating their visitors or sales that may be happening or the launch of a new product. If you rarely change these banners then repeat visitors will tend to start to ignore them. If you use them for placement of events or sales then you may find they are clicked through a lot more.
IF you have your banners on an auto scroll you need to get the timing right, you need to allow enough time for the banners to be read and clicked if needed but not too much time that the visitor leaves the page. Always give the visitor the opportunity to click through from banner to banner so if they miss one they can go back without having to wait for it to come round again.
Think very carefully about wording and images that you use on your banners as if done correctly they can very quickly improve conversion rates and sales.