.mwe-popups-overlay { background-color: rgba( 255, 255, 255, 0.9 ); z-index: 999; position: fixed; height: 100%; width: 100%; top: 0; bottom: 0; left: 0; right: 0; // flexbox to vertically/horizontally center children display: flex; justify-content: center; align-items: center; }