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.
This is usually the cheapest form of banner advertising, but also typically the least effective. Your banner ad will be displayed throughout the web site without regard to category or any form of targeting. This form of advertising is most appropriate for general use/interest types of products or services.
Scheduling of Internet advertising whereby ads run across an entire site, often at a lower cost to the advertiser than the purchase of specific site sub-sections (Source: IAB)
means a banner advertisement will appear anywhere on a website. (As opposed to run of category, ROC, which would appear only on pages within a specific category)