Prague-Austria

1. I don't know any low cost airlines travelling from Prague to Vienna (or another Austrian city).

2. You cannot take+ the euro-rail. That's a pass. Sorry if I sound picky, but you can +buy+ the Eurorail pass (something which I believe most people here will not recommend) and you can +take the train. There might be also some buses, but am no expert so I cannot really advise, sorry.

3. I personally dislike the use of the word "doing" when talking about countries/cities to visit. However, Bratislava is not in Austria and, for what my opinion matters, I would not want to visit 4 places in 5 days (and especially one place like Vienna which deserves at least 3 days to my view). I was happy with spending one day in Innsbruck. I've never been to Salzburg, but when I go, I'll make sure to spend two days. I'll go to Bratislava next week for the first time, but before I'm back and give you my opinion, dozens of other posters will have either told you how long you should spend there or suggested that you drop it for lack of time...

4. Cannot advise.

5. For accommodation, have a look at http://www.booking.com. If you state a budget, people might recommend something more specific.

6. About couchsurfing, I invite you to read #1 and #8 in this thread: http://www.lonelyplanet.com/thorntree/message.jspa?messageID=16187346. If you have the right reasons, then I highly recommend that you join.

yes, train from Vienna to Prague is about 4 hours and €60 sounds about right.
get it from the Austrian Rail site (obee? something like that, just google it, the english search is very obvious and easy).
I did this train trip last year and it was fine.

where are you starting your trip?
what you've suggested is a good loop, but travel between each place is a good 2ish hours each leg, so you'd spend half a day between one hotel and your next. be sure to consider this in your time plans...

click4sky flies from Prague to Bratislava. But given that the train is only about four hours, it doesn't make sense to fly.

1./2. the homepage of the train company is www.oebb.at; the cities you are planning to visit are rather close, so the train seems faster to me than flying (airports other than train stations are usually outside of the centers, and check-in and waiting for your luggage take some time too)

1. I would definitely reduce the amount of places! I would skip Bratislava (I've not been there myself, but many say it's similar to Vienna, but smaller), and go for either Salzburg or Innsbruck
   If after Prague and Vienna you can't wait to see more monuments go to Salzburg.
   If you would like to take a cable car up the mountains and stay in beautiful mountain scenery go to Innsbruck.

2. There might be snow, but of course no guarantee. If you need to see snow you can reach the glacier from Innsbruck in about an hour by public transport and then take the cable car up. You can also ski there.

At this time of the year the Christmas markets start in all of the cities you are going to visit. You might enjoy them.

The train certainly makes more sense and will give you a chance to observe the countryside and topography of these countries as you go along...as stated above you're trying to do too much in 5 days in Austria...if you have 9/10 days I would suggest 2/3 in Prague, 3 in Vienna, 2 in Salzburg and 2 in Cesky Krumlov travelling by train in that direction...I'm presuming by this you're arriving in Prague, of course...after 2 full days in Vienna you could decide then if you wish to spend the 3rd as a day-trip in Bratislava (which is nothing like Vienna as stated in #4 above!)...

There are loads of BnBs plus apartments & guesthouses with reviews on the the main hostel booking sites; Hostelworld, Hostelz and Hostelbookers which may help you settle on something...not sure how suitable couchsurfing is for a couple in these cities on a short time-frame like yours'...you might be better in a centrally located hostel/guesthouse...

There are limited cheap tickets for the train between prague and vienna. If you book early you might be lucky and get one. No low-cost-flights on this route.

OEBB Sprschiene

And I would skip bratislava (by the way, this is slovakia and not austria) as well. It's a very nice small town, but it's completly impossible to see these 4 citys in five days and Bratislava is the least impressive. If I were you I would also skip Salzburg because of your limited time (Vienna has a lot more to offer than Salzburg and Innsbruck will give you the additional mountain scenery).

Have fun

Thank you all so much. Really appreciate the suggestions!
Yes, will take the train... and reduce the places in Austria:)

Thanks makimaki...yes I know Bratislava is Slovakia...just put it on the same thread as its part of my trip (well, atleast in the planning stage it was:)
After all your suggestions, will def do a rain check on the no. of cities to visit!

If I were you I would also skip Salzburg because of your limited time (Vienna has a lot more to offer than Salzburg and Innsbruck will give you the additional mountain scenery).

Well, if you've only got 9/10 days for this itinerary, travelling by public transport and intending to visit Cesky Krumlov as well then I would respectfully suggest Innsbruck is totally out of your way...really Salzburg has far more to do and see and the mountains are just a short spin in any direction, more or less, out of the city...