If a request cannot be completed successfully, the server will either return an error image or an HTTP response status other than 200 together with an error message.
The response status value depends on the type of the error; for most common errors it is '403'. Error responses for non-image request types conform to the format specified with req= . (May not be consistently implemented at this time.)
The amount of detail included in the error message is configurable with attribute::ErrorDetail .
Image Serving can be configured to return error messages rendered into an image.
See attribute::ErrorImage in the image catalog reference for details.
If the error image is successfully generated, the HTTP response status is 200. If an error occurs when processing the error image, the standard HTTP error response and text message is returned to the client.
Image Serving can be configured to substitute a missing image with a default image. The default image can be specified either with attribute::DefaultImage or the defaultImage= command.