Different Style Sheet Based on Session

I’m trying to have a different style sheet displayed with different session id’s. In other words if someone goes here: http://www.website.com they get the default one if they go here http://www.website.com/?id=10 they get another one. I’ve got it working except one you click on another page it breaks, the session isn’t stored. Here is the code I have so far:

in the wp-config.php:

session_start();

in the header.php:

$_SESSION['id'] = $_GET['id'];
if ($_SESSION['id']=="10") { ?>
<link rel="stylesheet" href="<?php bloginfo('url'); ?>/wp-content/themes/default/style1.css" type="text/css" media="screen" />
<?php
}
else { ?>
<link rel="stylesheet" href="<?php bloginfo('stylesheet_url'); ?>" type="text/css" media="screen" />
<?php } ?>

Any help would be great.