i am a bit lost track with the MDN docs.
https://developer.mozilla.org/en-US/docs/Web/Reference/Events/readystatechange
In the above onreadystatechange specification, it says "HTML5". So does it mean onreadystatechange is a HTML5 event, and pre-HTML5 browsers should not understand it? However, i have tested in IE6 (through IE Tester), it works like in my latest Firefox.
So it is confusing. Thanks for any inputs.