body{
    margin: 0;
}
h1{
    margin: 0;
    color: white;
}
.header{
    width: 100vw;
    text-align: center;
    margin: 0;
    background-color: slategrey;
}
.fixed{
    position: fixed;
}
@media only screen and (max-width: 767px){
    .header{
        position: fixed;
    }
    .fixed{
        position: relative;
    }
}