let label_input input =
        match input with 
        | User_load_in_new_win_event(url) -> L
        | User_load_in_win_event(user_window, url) -> L
        | User_link_to_new_win_event(user_window, url) -> level_of_url url
        | User_link_to_named_win_event(user_window, name, url) -> level_of_url url
        | User_close_win_event(user_window) -> L
        | User_input_text_event(user_textbox, text, _) -> begin
               match user_textbox with 
               | User_textbox(user_window, nat) ->                              
                     match user_window with 
                     | User_window(url, nat2) -> level_of_url url
                end      
        | User_click_button_event(user_button) -> H
        | Network_response_event(net_conn, resp) ->  
                        M(domain_of_net_connection net_conn)