In the XMLHttpRequest Spec it says that: The DONE state has an associated error flag that indicates some type of network error or abortion. It can be either true or false and has an initial value of false. Also says something similar about a "send() flag" in an "OPENED" state. It's said in the specification but not in the IDL and when I create a new XMLHttpRequest I can't find those "flags". Where are those boolean variables?