My Code

function mysite_kill_rss() {
    wp_die( __('No feeds available, please visit our <a href="'. get_bloginfo('url') .'">homepage</a>!') );
  }

add_action('do_feed', 'mysite_kill_rss', 1);
add_action('do_feed_rdf', 'mysite_kill_rss', 1);
add_action('do_feed_rss', 'mysite_kill_rss', 1);
add_action('do_feed_rss2', 'mysite_kill_rss', 1);
add_action('do_feed_atom', 'mysite_kill_rss', 1);