footer {
    padding-left: calc(50% - 600px);
    padding-right: calc(50% - 600px);
    padding-top: 40px;
    padding-bottom: 40px;
    width: 100%;
    margin-left: auto;
    margin-right: auto;
    margin-top: auto;
    background-color: aliceblue;
    box-sizing: border-box;
}