How to set the div to adapt to changes in screen size? _html/css_WEB-ITnose

rt, there is another issue that needs attention:
The height of the header on the top of the page is fixed, while the height or width of the map area below changes.
I set the height and width to 100%, and set overflow to hidden in body{}. But the following problem occurred.

That is, there is a part below that is not displayed, and the part that is not shown is exactly equal to the height of the header.
How to set it up so that the div of the map can be displayed normally?

Reply to the discussion (solution)

Use absolute certainty to match position absolution

Use absolute certainty to match position absolution

I tried it, but it doesn’t work. There is no other way, I can only use jQuery to calculate. Thank you