/* https://www.w3schools.com/howto/howto_css_center-vertical.asp  */

body {
    background-color: aliceblue; /* Same used in site css also */
}

.centerdiv {    
    position: absolute;
    top: 40%;
    left: 50%;
    transform: translate(-50%, -40%);
    padding: 10px;
}

.footerdiv {
    position: fixed;
    left: 0;
    bottom: 0;
    width: 100%;
    color: white;
    text-align: center;
    padding: 10px;
}

@media (max-width: 450px) {
    .centerdiv {
        position: unset;
        top: 0;
        left: 0;
        transform: translate(0, 0);
        margin: 10px;
    }

    .footerdiv {
        position: unset;
        margin-top: 15px;
    }
}