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

header {
  background-color: #00008b;
  color: #f0ffff ;
  padding: 10px;
}

h1 {
  margin: 0;
}

nav ul {
  list-style-type: none;
  padding: 0;
text-align: right;
  <li><a href="index.html">To ????????????</a></li>
        
<li><a href="about.html">????? ???????</a></li>
        
<li><a href="courses.html">?????? ???????</a></li>
        
<li><a href="contact.html">???????????</a></li>

}

nav ul li {
  display: inline;
  margin-right: 10px;

}

nav ul li a {
  color: #f0ffff ;
  text-decoration: none;
}

main {
  padding: 20px;
}

footer {
  background-color: #00008b;
  color: #fff;
  padding: 20px;
  text-align: center;
}