I used this site extensively in preparation for my current trip to Paris. We got in late last night to CDG, and were planning on taking the RER B and then switching to the RER A train to reach our hotel right near the Arc de Triomphe. This was in fact the instructions in the confirmation mail from the hotel.
However to our dismay when we reached the RER A platform at Chatelet Les Halles, it seemed from the signs that the A line is not running July 25-Aug 23 2015 between Auber and La Defense stations, i.e. not stopping at Arc de Triomphe..
So I thought it would be a good idea to let people here know about this!