See the following snippet, is this what you want?
body {
background: silver;
padding: 0 10px;
}
#content:after {
height: 10px;
display: block;
width: 100px;
background: #808080;
border-right: 1px white;
content: '';
}
#footer:before {
display: block;
content: '';
background: silver;
height: 10px;
margin-top: -20px;
margin-left: 101px;
}
#content {
background: white;
}
#footer {
padding-top: 10px;
background: #404040;
}
p {
padding: 100px;
text-align: center;
}
#footer p {
color: white;
}<body>
<div id="content"><p>#content</p></div>
<div id="footer"><p>#footer</p></div>
</body>