try this may work header.php page will be
<!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>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Untitled Document</title>
<link href="css/ssHeadFoot.css" rel="stylesheet" type="text/css" />
</head>
<body>
<!-- the other code for this page -->
and the main page will be
<?php include 'header.php'; ?>
</body>
</html>
some times it's work with me when do this
and try use require_once for the page so when the header.php is missing the code stop and if you include it again no error appear or page require twice