<!DOCTYPE html>
<html>
<head>
<style type='text/css'>
html, body {
height: 100%;
padding: 0;
margin: 0;
}
body {
padding-top: 100px;
background-color: gray;
}
header, footer {
width: 100%;
height: 100px;
padding: 0;
margin: 0;
}
header {
position: absolute;
top: 0;
left: 0;
background-color: red;
}
.main-content {
width: 100%;
height: 100%;
background-color: gold;
}
footer {
background-color: green;
}
</style>
</head>
<body>
<header>
<h1>Header</h1>
</header>
<div class="main-content">Main Content</div>
<footer>Footer</footer>
</body>
</html>