An issue you may be having is you're calling session_start() after you've outputted some HTML to the browser. If you're using cookie based sessions (which I'm assuming you are), then the session_start call should be
before anything is outputted to the browser. A good way of ensuring this is to make it the very first thing your PHP script does, i.e. removing the session_start call from auth.php and changing the first line of home .php from:
to
Code:
<?
session_start();
Hope this helps!