/* professional, and standard header keep the design simple and clean. keep the structure responsive.*/
body {
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
  background-color: #f4f4f4;
}
header {
  background-color: #333;
  color: #fff;
  padding: 20px 0;
  text-align: center;
}
/* design the navigation bar*/
nav ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  display: flex;
  justify-content: center;
}

nav {
  display: flex;
  justify-content: center;
  background-color: #444;
}

nav a {
  color: #fff;
  padding: 14px 20px;
  text-decoration: none;
  text-align: center;
}
nav a:hover {
  background-color: #555;
}
main {
  padding: 20px;
}