body {
  font-family: Arial, sans-serif;
  background: #fff;
  color: #333;
  margin: 0;
  padding: 0;
}
#top-menu, #footer {
  background-color: #f4f4f4;
  padding: 10px;
}
#header {
  text-align: center;
  padding: 20px 0;
}
#container {
  display: flex;
  flex-wrap: wrap;
  padding: 10px;
}
#left, #right {
  width: 20%;
  padding: 10px;
}
#content {
  width: 60%;
  padding: 10px;
}
@media screen and (max-width: 768px) {
  #left, #right, #content {
    width: 100%;
  }
}