DOMNodeInserted is deprecated in the DOM Level 3 Events recommendation, along with all the other mutation events:
http://www.w3.org/TR/DOM-Level-3-Events/#event-type-DOMNodeI...
They have been deprecated because they perform poorly:
> Firefox, for example, when it realizes that a mutation event has been turned on, instantly goes into an incredibly-slow code path where it has to fire events at every single DOM modification. This means that doing something like .innerHTML = "foo" where it wipes out 1000 elements would fire, at least 1000 + 1 events (1000 removal events, 1 addition event).
http://lists.w3.org/Archives/Public/www-dom/2009AprJun/0072....
> Mutation Events are widely acknowledged as “slow” in terms of the real performance degradation that occurs on websites that use them heavily for tracking changes to the DOM