body{
   background-color: #09aa09;
}
header h1{
   text-align: center;
}

nav, footer, .content, div, header{
   border: 0;
   margin: 0;
   padding: 0;
}

nav > ul{
   list-style: none;
   background-color: teal;
   display: block;
}
nav > ul li{
   display: inline-block;
   padding-right: .25em;
}
a:link{
   color: blue;
}
a:visited{
   color: orange;
}
a:hover{
   color: purple;
}
a:active{
   color: yellow;
}
footer{
   background-color: grey;
   font-size: 1em;
   display: inline;
}

#thumbnail{
   height: 150px;
   width: 200px;
}
.content{
   font-family: Arial, Helvetica, sans-serif;
   font-size: 2em;
   color:#004d00;
   background-color: #d3d3d3;
}

/* additional rules */
.caption{
   font-size: .50em;
}
.caption>a, .caption>a:link{
   color: #2e8b57;
   text-decoration: none;
}
.caption>a:active{
   color: #ffff66;
}
.contact{
   padding: 0;
   border: 0;
   margin: 0;
}
div > p.caption{
   padding: 0;
   border: 0;
   margin: 0;
}
article{
   display: block;
   min-height: 400px;
}
nav{
   position: -webkit-sticky;
   position: sticky;
   top: 0;
   display: inline-block;
}