header {
  background-color: blue;
  color: white;
  text-align: center;
  padding: 5px;
}

nav {
  background-color: yellow;
  padding: 7px;
}

section {
  padding: 15px;
  margin: 10px;
  width: 300px;
  float: left;
}

aside {
  background-color: blue;
  color: yellow;
  padding: 15px;
  margin: 10px 0px 10px 350px;
}

footer {
  background-color: red;
  color: white;
  clear: both;
  text-align: center;
  padding: 5px;
}

#allcontent {
  width: 840px;
  margin-left: auto;
  margin-right: auto;
}