html {
    background-image: url("https://th.bing.com/th/id/OIP.MKZk0Ul5i2mEm5yFAuPH6wHaIz?r=0&rs=1&pid=ImgDetMain");
    background-repeat: no-repeat;
    background-size: cover;
    background-position: center;
}

header {
    background-color: #ff74c0;
    border: 10px solid rgb(255, 226, 245);
    margin-left: auto;
    margin-right: auto;
}

body {
    background-color: #fff4fa;
    margin-left: auto;
    margin-right: auto;
    padding: 5px;
    width: 50%;
}

body > *:not(header) {
    margin: auto;
    width: 95%;
}

header > * {
    margin: auto;
    width: 95%;
}