2.2.3 Extended Error Handling
The current errors that are returned by the HTTP protocol are not sufficient to support all the error conditions that occur in file handling. This section specifies a mechanism to extend HTTP error handling by using the X-MSDAVEXT_ERROR header.
Extended error handling MAY be used by applications in order to provide more specific information to the application user for an error that occurred on the server. The X-MSDAVEXT_ERROR header, which is returned by the WebDAV server, MAY be included in any WebDAV server response.<7>
This new header uses the Augmented Backus-Naur Form (ABNF) syntax, as specified in [RFC2616] section 2.1, and is defined as follows:
MSError-Header = "X-MSDAVEXT_ERROR" ":" Extended-error "; " Error-string Extended-error = 1*DIGIT Error-string = 1*TEXT
An Extended-error is an implementation-specific number that provides additional information about the cause of the HTTP error.
An Error-string is a percentage-encoded UTF-8 string, as specified in [RFC3986] section 2.1, that gives additional explanatory text about the cause of the error. This string is not significant to protocol operation and is intended only for display and logging purposes.