Pagination is the system by which pages of a book, play, manuscript, or otherwise handwritten or printed document are marked with consecutive Arabic numbers to indicate the proper order of the pages. Pagination is very rarely found in documents pre-dating 1500, and only became common practice circa 1550, when it replaced foliation, which numbered only the front sides of folios. Pagination can also refer to the process of organizing information onto webpages. For instance, threads on a bulletin board might be paginated such that 20 appear on each page.