3. The navbar should always be at the top of the viewport. code example

Example: the navbar should always be at the top of the viewport

header {
  position: fixed;
  width: 100%;
  top: 0;
  left: 0;
  background-color: #cc0000;
  color: white;
  font-family: 'Exo 2', sans-serif;
  padding: 1em;
}