html, body {
    background: url(background.jpg) no-repeat center center fixed; 
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
    padding: 0;
    margin: 0;
    }

    body {
      text-align: center;
    }

    .parent {
      width: 30%;
      margin: 0 auto;
  }
    
    header{
    height: 25px;
    }
    header nav ul{
    display: flex;
    margin-left: 80%;
    }
    
    header nav ul li{
    padding-left: 10%;
    }