style.css

body {
    background-color: #e5ddd5;
    background-image: url(/img/sfondo-WA.png);
    margin: 0;
    font-size: 27px;
}

header {
    height: 100px;
    background-color: #00887a;
    text-align: center;
    box-shadow: 0 5px 5px grey;
}

header img {
    position: absolute;
    left: 10px;
    top: 25px;
    width: 50px;
}

header label {
    color: white;
    position: relative;
    top: 35px;
    text-shadow: 0 5px 5px black;
}

footer {
    padding: 0;
    height: 64px;
    margin-bottom: 10px;
}

#msg {
    position: absolute;
    width: inherit;
    height: 50px;
    top: 50%;
    margin-top: -25px;
    border-radius: 20px;
    padding: 10px;
    font-size: medium;
    outline: none;
}

#btn {
    height: 64px;
    background-image: url('img/button.png');
    background-size: contain;
    background-position: center center;
    background-repeat: no-repeat;
}