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

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;