Above the fold
Above the fold means the content that can be seen on a web page before the user starts to scroll. It originates from the print industry, where above the fold meant the top half of a front page on a folded newspaper.
The position of the "fold" depends on what device the user is on. As screen sizes vary drastically there is no set definition for the number of pixels that define the fold. This is because different screen resolutions will show different portions of the website without scrolling. Further complicating matters, many websites adjust their layout based on the size of the browser window, such that the fold is not a static feature of the page.
In general, it can be said that whatever is above the fold on the page, gets more attention than what's below the fold. However, the term is subject to controversy as we see studies confirming and debunking the folds' influence on user behaviour.
Let's make sure the call to action is visible above the fold