ad buying option in which ad placements may appear on any pages of the target site.
ROS describes a media placement that covers the whole site, not a targeted page, channel or section. As a result a banner that is served on a ROS basis can appear on any part of the site that carries banners.
Advertising that is not targeted to a specific topic on a site. Run of site advertising is usually cheaper than targeted advertising because it can be used to fill unsold inventory. Run of site advertising is best used for products and services that appeal to the vast majority of users.