1.box {
2  width: 50px;
3  height: 50px;
4}
5.yellow {
6  background: yellow;
7  position: absolute;
8  top: 50%;
9  left: 50%;
10  transform: translate(-50%, -50%);
11}
12body {
13  background-color: black;
14}

1function initialSetup() {
2  if (document.getElementById("yellow") != null) {
3    document.getElementById('yellow').style.visibility = 'hidden';
4    setTimeout("document.getElementById('yellow').style.visibility = 'visible'", 2000);
5  }