body {
  background-color: lightyellow;
  font-family: Arial, Helvetica, sans-serif;
  width: 80%;
  margin: 0 auto;
  padding: 20px;
}

h1 {
  color: darkblue;
}

h2 {
  color: darkgreen;
}

h3 {
  color: darkred;
}

p {
  color: black;
  font-size: 16px;
}

#mainTitle {
  text-align: center;
  color: green;
}

.highlight {
  color: red;
  font-weight: bold;
}

#allcontent {
  width: 700px;
  margin-left: auto;
  margin-right: auto;
  padding: 20px;
  text-align: center;
}

header img {
  max-width: 100%;
  height: auto;
  border: 2px solid gray;
  margin-top: 10px;
}

nav ul {
  list-style: none;
  padding: 0;
  margin: 10px 0 20px 0;
}

nav li {
  display: inline-block;
  margin: 0 10px;
}

main {
  padding: 10px;
}

section {
  margin-bottom: 20px;
}

article {
  margin-bottom: 20px;
}

aside {
  padding: 10px;
  margin-top: 20px;
  border-top: 1px solid #ccc;
}

footer {
  margin-top: 20px;
}

img {
  border: 2px solid gray;
  max-width: 100%;
  height: auto;
}

video {
  max-width: 100%;
  height: auto;
}

audio {
  width: 100%;
  max-width: 400px;
}

a {
  color: blue;
}