html, body, nav ul{
   padding: 0;
    margin: 0;
}

ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  overflow: hidden;
  background-color: #333;
}

li {
  float: left;
}

li a {
  display: block;
  color: rgb(255, 0, 0);
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
}

li a:hover {
  background-color: #ff0000;
}

body {
background-color: blue;
}

header  {
    background-color: magenta
}