Obsolete since Gecko 13.0 (Firefox 13.0 / Thunderbird 13.0 / SeaMonkey 2.10)
This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.
The nsIDOMFileError interface describes errors that occur while using the DOM File API. It implements the DOM FileError object; for details, please read that article.