onerror Event for <img>

Does any one know why the onerror event is not included in the current HTML
standards?

An example of this code, which appears to work in Netscape 3+ and IE 4+, is
this:

	<img alt="My Image" src="someimage.gif" onerror="alert('File Not
Found')" />

Any feedback would be greatly appreciated.

Thanks.

Rick Roth
Web Development
Rivio, Inc.
rickr@rivio.com