* {
  box-sizing: border-box;
}

body {
  font-family: Arial, Helvetica, sans-serif;
  color: #333333;
}

header {
  background-color: #ffffff;
  padding-top: 1px;
  padding-bottom: 1px;
  text-align: left;
  padding-left: 10%;
  font-size: 35px;
  color: white;
}

nav {
  float: left;
  width: 30%;
  height: 300px;
  background: #ccc;
  padding: 5%;
}

link {
  color: #00b285;
}

nav ul {
  list-style-type: none;
  padding: 0;
  
}

article {
  float: left;
  padding: 20px;
  width: 70%;
  background-color: #f4f4f4 ;
  height: 300px;
}

section:after {
  content: "";
  display: table;
  clear: both;
}

footer {
  background-color: #777;
  padding: 10px;
  text-align: center;
  color: white;
}

@media (max-width: 600px) {
  nav, article {
    width: 100%;
    height: auto;
  }
}