A block ad is an optional, add-on service to the basic listing of always-free eBooks. You should purchase a block ad if you’d like more exposure for your eBook, even after other eBooks are posted and push your listing off the homepage.
A button ad is 250px wide and 250px high, and it appears in the sidebar of almost every post and page.
Block ads do not rotate and show at all times, unless the post or page does not show the right sidebar.
Block ads appear in the sidebar for 15 days or 30 days and can be extended, but they do not auto-renew.