404. That’s an error.

The requested URL /catalog/product_compare/add/product/318/uenc/aHR0cDovL2NsZWFudHVuaW5nLmNvbS9hcHBsZS1pcGhvbmUtM2ctY2FyYm9uLWZpYmVyLWNhc2UtY292ZXItcHJvdGVjdGlvbi1zY29waW9uZS5odG1s/ was not found on this server. That’s all we know.