.cssDisclaimerHeader {
    position: absolute;
    top: 160px;
    left: calc(50% - 250px);
    width: 500px;
    color: white;
    background-color: transparent;
    border: 0px none transparent;
    text-align: center;
}
.cssDisclaimerBox {
    box-sizing: border-box;
    width: 800px;
    height: calc(100% - 373px);
    max-width: 900px; /* keep it readable */
    margin: 250px auto 153px; /* top / horizontal auto / bottom */
    padding: 18px;
    background-color: #fff; /* change as you like */
    border: 15px solid white;
    border-radius: 12px;
    overflow-y: auto;
}