Here we start seeing the separations of element behaviors from the DOM-Element; DOM-Elements and their behaviors cab be connected using  selectors to element-id or css-classes.

/* CSS layout */
#left_col {
width: 200px;
position: absolute;
left: 0px;
top: 0px;
}

#right_col {
width: 200px;
position: absolute;
top: 0px;
right: 0px;
}

#page_content {
margin-right: 200px;
margin-left: 200px;
}

#container {
position: relative;
width: 100%;
}
 

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html dir="ltr" xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Untitled 1</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<link rel="stylesheet" type="text/css" href="Untitled_1.css" />
</head>
<body>
<div id="container">
<div id="left_col">
</div>
<div id="page_content">
</div>
<div id="right_col">
</div>
</div>
</body>

</html>