style.css

*+* {
    box-sizing: border-box;
    font-family: Lato, Arial, Helvetica, sans-serif
}

body {
    margin: 0;
}

#nav-content-footer-template {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

#nav-content-footer-template>nav {
    height: 100px;
    background-color: #abc;
}

#nav-content-footer-template>#page-body {
    flex: 1;
}

#nav-content-footer-template>footer {
    height: 200px;
    background-color: #679;
}