Search engines like Google have multiple indices where web pages are stored. When a web site is removed from the main index, it is indexed in a supplemental index. These sites could be sites that have not been updated or attracted much traffic over a period of time, have duplicate content to other sites, and for other reasons are not considered reliable, trustworthy, or relevant.

If a company neglects their web site to the point where it is shuffled to a supplemental index, a considerable effort will be required to revive that site's reputation for it to return to the main indices. In some cases, the only viable option is to scrap the old site and URL, and launch an entirely different new site and URL.  However traditionally pages that are placed in Google's supplemental index can re-enter the main index if the indexing issues are corrected.  (Removing duplicate content, updating the page content, updating the links to the page et al.)