Page header running header or running headline, is a header that appears on each standard page. Running heads do not usually appear on display pages such as title pages, or on other front or back matter. Running heads in a book typically consist of the title on the left-hand (verso) page, and the chapter title on the right-hand (recto) page; or the chapter title on the verso and subsection title/subhead on the recto, aiding the reader's navigation by showing what content exists within the two-page spread at hand. A special case of the latter is in dictionaries, whose running heads are called
Page numbering way as their printed counterparts. While reading devices for reflowable documents such as EPUB e-books may display page numbers, these numbers change from device to device depending on factors such as the size of the display and the selected font size. This makes them unsuitable for citation purposes. To remedy this problem, Amazon Kindle e-books contain what are called "location numbers", that is, numbers in the margin of the electronic text that indicate where the corresponding page begins in the printed version of the book. In codicology, each physical sheet ("folium", abbreviated "fol." or "f.") of a manuscript is numbered,