Question

I need solution to emulate fixed position, but relative parent div, not whole viewport. JS solutions are laggy. I need fixed related parent container, because if window has small height, div with fixed position enters into footer zone.

Example

Answer 1

Another approach re your update.

Try giving the fixed div z-index: 10;

And the footer div position: relative; z-index: 11

That should make the footer overlap the fixed div.