body {
    background: lightblue;
    font-family: inherit;
    margin: 20px auto;
    width: 800px;
}
header {
    background: #78B6B8;
    padding: 20px;
}
h1 {
    color: white;
    font-family: sans-serif;
    margin: 0;
    text-align: center;
}
nav {
    padding: 0 20px;
    background: #4ca3dd;
    text-align: center;
}
nav a {
    display: inline-block;
    text-decoration: none;
    color: white;
    background: #00CED1;
    padding: 5px 10px;
}
nav a.active {
    background: #468499;
}
nav a:hover {
    background: blue;
}
main {
    background: white;
    padding: 20px;
    overflow: auto;
    min-height: 600px;
}
main h2 {
    margin: 0;
}
main img {
    width: 50%;
    text-align: center
}
footer {
    text-align: left;
    padding: 20px;
}
.center {
  display: block;
  margin-left: auto;
  margin-right: auto;
  width: 50%;
}