For a personal footer in the admin section. Add this to the function.php file of your theme
add_filter( 'admin_footer_text', 'my_admin_footer_text' );
function my_admin_footer_text( $default_text ) {
return '<span id="footer-thankyou">Website by <a href="http://www.yoursite.com">yoursite</a><span> | Powered by <a href="http://www.wordpress.org">WordPress</a>';
}