body  {
  background: #333333;
  margin: 0px;
  padding: 0px; 
}

nav {
  box-sizing: border-box; 
  width: 300px; 
  height: 400px; 
  background: #1F3B6F; 
  float: left; 
  margin-right: 20px; 
  border-radius: 0px 20px 20px 0px; 
  padding: 10px; 
}

aside {
  box-sizing: border-box;
  width: 300px;
  height: 400px;
  background: #1F3B6F;
  float: right;
  margin-left: 20px;
  border-radius: 20px 0px 0px 20px;
  padding: 10px;
}

body > header {
  position: fixed;
  top: 0px;
  width: 100%;
  height: 40px;
  background: #aaaaaa;
  background-image: linear-gradient(45deg, black, red, yellow);
  color: #485a91;
  text-align: center;
}

footer {
  background: #ff8800;
}

body > footer {
  position: fixed;
  bottom: 0px;
  width: 100%;
  height: 40px;
  background: #aaaaaa;
  background-image: linear-gradient(45deg, black 33%, red 33%, red 66%, yellow 66%);
  color: #485a91;
  text-align: center;
}

section {
  border: 1px solid #ffff00;
  border-radius: 5px;
  padding-bottom: 0px;
}
      
p, h1, h2 {
  margin: 0px;
}

header + p {
  margin: 40px;
}

.block {
  text-align: justify;
}

main {
  position: fixed;
  top: 40px;
  width: 100%;
  height: calc(100% - 80px);
  display: block;
  background: #485a91;
  overflow: auto;
  scrollbar-base-color: #99CC99;
}