404. That’s an error.

The requested URL /catalog/product_compare/add/product/5987/uenc/aHR0cDovL3d3dy5idXlpbmdmdXJuaXR1cmUuY28udWsvZGluaW5nLXJvb20vZGluaW5nLWNoYWlycw,,/form_key/aKJuguxaXkM21c6y/ was not found on this server. That’s all we know.