body 
{
    font-family: Arial, sans-serif;
    line-height: 1.6;
    margin: 0;
    padding: 0;
}

header 
{
    background-color: green;
    color: #fff;
    text-align: center;
    padding: 1;
}

.center 
{
    display: block;
    margin-left: auto;
    margin-right: auto;
    width: 50%;
}