Vincent, I'll answer again using your new requirements. Since you don't care about the content being hidden if it's too long, you don't need to float the header. Just put overflow hidden on the html and body tags, and set #content
height to 100%. The content will always be longer than the viewport by the height of the header, but it'll be hidden and won't cause scrollbars.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Test</title>
<style type="text/css">
body, html {
height: 100%;
margin: 0;
padding: 0;
overflow: hidden;
color: #FFF;
}
p {
margin: 0;
}
#header {
background: red;
}
#content {
position: relative;
height: 100%;
background: blue;
}
#content #positioned {
position: absolute;
top: 0;
right: 0;
}
</style>
</head>
<body>
<div id="header">
Header
<p>Header stuff</p>
</div>
<div id="content">
Content
<p>Content stuff</p>
<div id="positioned">Positioned Content</div>
</div>
</body>
</html>