Customizing the dashboard page or post overview

I use a version of the following, to add text to the top of the Page (edit.php?post_type=page):

// Show message when viewing pages
function page_AdminMessage()
{
    showMessage("You are now viewing the Pages", false);
}
if ($_GET['post_type'] == 'page') {
    add_action('admin_notices', 'page_AdminMessage');
}

Which just needs to be added into functions.php.