A div block appears on the page, and so that it appears in any part of the long page, it is given the position fixed. The height of this block can be different, depending on the text content being viewed, and if the block goes beyond the screen, it can no longer be scrolled, only the main page is scrolled.
What parameters to set to get the opposite effect: scroll the inf block div block, and the main page to stand still? The block itself appears with the help of Js, when clicking on certain areas, it is given the value of display:block , by default: none .