Why does the Div appear at the end of the site?

Question

css

Expensive time of day, the problem occurs after submitting the form, a window appears that the form was successfully or unsuccessfully sent, for 1 second and after that this appears.


At the same time, some content shifts up and the site scroll disappears.
Thank you for your attention

Answer 1

By class, it is obvious that this is a modal window shadow block. The class structure is similar to Bootstrap's. Scrolling disappears because the script activates the modal window and hangs a class with overflow: hidden on the body. The shadow box is generated automatically by Bootstrap's JS.
You are clearly closing the modal window incorrectly. Probably just with display: none or some kind of fadeIn(). Then, the content of the individual window disappears from the screens, but all utility classes and the shadow element remain active.
Closing a modal in Bootstrap goes like this ( documentation link ):
$('#IDмодального').modal('hide');