<!DOCTYPE HTML>
<html>
<head>
<style>
div.main {
border: 5px solid #111;
display: table;
height: 500px;
width: 500px;
}
div.main > div {
display: table-row;
}
div.header {
background: blue;
height: 100px;
}
div.content {
background: red;
/*height: 100%;*/
}
div.footer {
background: green;
height: 100px;
}
</style>
</head>
<body>
<div class="main">
<div class="header">Header</div>
<div class="content">Content</div>
<div class="footer">Footer</div>
</div>
</body>
</html>