* {
  font-size: 18px;
  font-family: "MS Serif";
  margin: 0;
  padding: 0;
  list-style: square;
  text-decoration: none;
}

#container{
  width: 84%;
  max-width: 1280px;
  margin: 0 auto;
}

header {
   position:relative;
   height: 8rem;
   background: #003366;
   box-shadow: 0 4px 0.3125rem rgba(0,0,0,.3);
 }

  header h1{
    letter-spacing: 3px;  /*  文字の間 */
    position: absolute;
    top: 3rem;
    left: 3rem;
    font-size: 2rem;
    color: white;
 }

nav {
  letter-spacing: 1px;  /*  文字の間 */
  line-height: 2rem;   /*   行間 */
  padding: 1.5rem 2.5rem ;
  background: #007ab5;
}

  nav ul li{
    margin-right: 2rem;
  }
  nav ul li a {
    color: white;
  }

main{
  display: flex;
  flex-wrap：wrap;
  justify-content:space-between;
}

  section{
    flex: 5;
    padding: 1rem;
    background: #d9e3ee;
  }

    article{
      min-height: 8rem;
      padding: 1rem;
      margin-bottom: 1rem;
      background: #FFF;
    }

  aside{
    flex: 1;
    padding: 1rem;
    background: white;
  }

footer {
  padding: 1.5rem 3rem;
  text-align: center;
  background: #003366;
  color: white;
}

/*   margin　境界線の外側の余白
     border　境界線
     padding　境界線の内側の余白
     width, height　幅と高さ    */