Код:
* {margin: 0px; padding: 0px;}
html {height: 100%;}
body {background: #FFFFFF; min-width: 1000px; min-height: 100%; position: relative;}
* html body {height: 100%;}

#header {height: 100px;}
#content {padding-bottom: 100px;}
#footer {width: 100%; height: 100px; position: absolute; bottom: 0px;}
Код:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>***</title>
</head>
<body>
<div id="header"></div>
<div id="content"></div>
<div id="footer"></div>
</body>
</html>
Учите матчасть. )