A graphical advertising unit, smaller than a banner ad.
Button ads come in a variety of sizes. There are standards such as 120×90, 120×60, 125×125 and 88×31 (micro-button), although nonstandard button ads are not uncommon. Whereas banners are often placed at the top or bottom of a page, buttons are often placed towards the middle of a page on the left or right sides.
see also: Digital Marketing Tools