#banner {
  background-color: #1a1a2e;
  text-align: center;
}

header {
  background-image: url('https://upload.wikimedia.org/wikipedia/commons/thumb/9/97/The_Earth_seen_from_Apollo_17.jpg/1280px-The_Earth_seen_from_Apollo_17.jpg');
  background-repeat: no-repeat;
  color: white;
  background-size: cover;
  background-position: center;
  padding: 30px;
  text-shadow: 2px 2px 6px black;
}

#banner h1 { color: white; }
#banner h2 { color: #f0f0f0; }
#banner a { color: #aee8ff; }
```

So your `beta_testing` folder should have these files:
```
beta_testing/
├── page1.html
├── page2.html
├── aboutme.html
├── common.css
└── Banner.css