404. That’s an error.

The requested URL /catalog/product_compare/add/product/1640/uenc/aHR0cDovL2pvc2VhbGRvLmNvbS5ici9jYXNhLWUtZGVjb3JhYy1vL3JlbG9naW9zLWRlLW1lc2EuaHRtbA,,/form_key/G2cfkcRYhmoFZfEM/ was not found on this server. That’s all we know.