404. That’s an error.

The requested URL /catalog/product_compare/add/product/2300/uenc/aHR0cDovL3d3dy50aHJvd21lYXBpbGxvdy5jb20vdGFwZXN0cnktcGlsbG93L2NhdC1kZWNvci9jYXQtbmFwLmh0bWw,/ was not found on this server. That’s all we know.