Client Error Codes begin with the number 4, such as 404 or 403 (two of the most common client side errors). A Client Error Code indicates that there is an issue with the request, and that the request itself must be changed in order to get a different result.
For example, if you get a 404 error code, it means the resource you requested does not exist. The request may be incorrect or the resource may have been removed, but the server is functioning correctly and the error is that the user is requesting something that is not there.
