JSFiddle - React, Tailwind, and code Playground
HTML
<div id="felso"></div>
<div id="also"></div>CSS
body { background: gray; height: 100%; margin: 0; }
div { border: 1px solid yellow; }
#felso { height: 100px; background: red; }
#also { background: blue; position: absolute; top: 102px; bottom: 0; left: 0; right: 0; }