shurik_shink,
<body>
<style>
body {
position: relative;
margin: 0;
padding: 0;
min-height: 100%;
}
div {
border: 1px solid black;
width: 100%;
box-sizing: border-box;
text-align: center;
}
#header {
position: absolute;
top: 0;
height: 1.5em;
}
#content {
padding: 1.5em 0;
min-height: 100%;
}
#footer {
position: absolute;
bottom: 0;
height: 1.5em;
}
</style>
<div id="header">Header</div>
<div id="content">Content</div>
<div id="footer">Footer</div>
</body>