body {
  background-color: lightgray;
  font-family: Arial, Helvetica, sans-serif;
}


#container {
  width: 1100px;
  margin: 0px auto;
  border:4px solid gray;
}


header {
  background-color: red;
  height: 100px;
  width: 100%;
  margin: 0px;
  text-align: center;
  line-height:100px;
  color: antiquewhite;
  border-bottom: 2px solid black;
}


nav ul li {
  float: left;
  list-style: none;
  margin: 20px;
  line-height: 10px;
}


a {text-decoration: none;}

ul {text-align: center; display: inline-block;}


#content{
    float: left;
    width: calc(80% - 20px);
    background-color: green;
    min-height: 500px;
    padding: 10px;
}


.article {
  color: white;
  margin-top: 15px;
  margin-bottom: 15px;
  border-bottom: 1px solid white;
  padding-bottom: 20px;
}


aside{
    float: left;
    width: calc(20% - 20px);
    background-color: coral;
    min-height: 500px;
    padding: 10px;
}


footer{
    background-color: black;
    color: white;
    text-align: center;
    height: 30px;
    line-height: 30px;
}


.clearfix{
    clear:both;
}


* {
  margin: 0px;
  padding:0px;
}