What is ERC 404?

Could you please clarify what you mean by "ERC 404"? As I understand, there isn't a direct standard called ERC 404 in the Ethereum ecosystem. ERC stands for Ethereum Request for Comment, which are proposals for technical standards that the Ethereum community can use to build decentralized applications. Perhaps you're referring to a specific token or project that utilizes a similar naming convention or an error code that is not directly related to ERC standards? Could you please provide more context or details so I can give you a more accurate answer?