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: 50px;
  color: antiquewhite;
  border-bottom: 2px solid black;
  padding-top:10px;
  padding-bottom:0px;
}
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;
}