These events have never been valid HTML - they are proprietary IE events.
Check the documentation:
http://msdn.microsoft.com/workshop/a...electstart.asp
See the note under Standards Information near the bottom? " There is no public standard that applies to this event." Now check something like onClick, which is valid HTML/XHTML and it will tell you that "This event is defined in HTML 4.0".
You were never really preventing anyone who really wanted to steal your content from doing so anyway, you were just anoying some users who wanted to use the normal abilities of thier browser.
The only way to really protect your content, is to not publish it.