sorry, I don't know the online possibilities that AustrianRailways offers.
But you can get timetable informations, tickets and price informations through the swiss railway site (in english too):
http://www.rail.ch/index_e.htm
Travel / Timetable
http://www.rail.ch/pv/index_e.htm
Enter:
Departure: Vienna (it will be Wien Westbahnhof)
Destination: Salzburg
Travel Date: DD.MM.YYYY
Time: hh:mm Departure or Arrival
Start query
Click on
order (2nd class)
Click on send request at the bottom of the page, to get price informations before ordering by email (in my experience they will answer in the next 24 hours, on working days). (the information there says: Please contact me before issuing the tickets and tell me the price/reservations. You'll get an answer to your e-mail as soon as possible.)
The fastet trains will take about 2 hours 57 minutes