What is Above the fold? – Web Design

Many website mension this name, when topics is about Google Adsense.

From Wekipedia:

Read:

"Above the fold" is a graphic design concept that refers to the location of an important news story or a visually appealing photograph on the upper half of the front page of a newspaper, or in case of webpages, the part of a page that's visible without scrolling. Most papers are delivered and displayed to customers folded up, meaning that only the top half of the front page is visible. Thus, an item that is "above the fold" may be one that the editors feel will entice people to buy the paper.

Alternatively, it reflects a decision, on the part of the editors, that the article is one of the day's most important. By extension, the space above the fold is also preferred by advertisers, since it is the most prominent and visible even when the newspaper is on stands.

The term can be used more generally to refer to anything that is prominently displayed or of highest priority.
This term has been extended and used in web development to refer the portions of a webpage that can be visible without scrolling. However, some have suggested that this term is vague as screen sizes vary greatly between users, especially in an era where websites are viewed with mobile devices as much as home computers.