You can use this for client sites as a simple point of reference to contact you as the developer

Add contact details to WordPress dashnoard for clients

// Wordpress Custom Admin Footer
// customize admin footer text. Add this to functions.php
// Source http://wordpress.stackexchange.com/posts/6005/revisions
// Modified by Tahir Taous


// customize admin footer text Will be visible in Dashboard
function custom_admin_footer() {
        echo 'Created By <a href="//tahirtaous.com/contact">Tahir Taous</a> ';
} 
add_filter('admin_footer_text', 'custom_admin_footer');