.exactCenter {
    width:300px;
    height:300px;
    position: fixed;
    background-color: #3b3c3d;
    top: 50%;
    left: 50%;
    margin-top: -100px;
    margin-left: -100px;
    justify-content:center;
}
.exactCenter div{
    background-color: #3b3c3d;
    color:#fff;
    padding: 10px;
}