html {
    background-image: url(sfondo.jpg);
    background-size: cover;
    background-position: left top;
}
body{
    background-color: transparent;
}
.navbar-brand {
    background-image: url(logo.png);
    background-size: contain;
    background-repeat: no-repeat;
    width: 128px;
    height: 80px;
}
.navbar-brand span{
    visibility: hidden;
}
.container{
    background-color: rgba(255,255,255,0.8);
}

nav.navbar {
    padding: 0;
}
nav.navbar>div.container {
    margin: 8px:
}