I want to travel from Weyer to Salzburg, is it cheaper to go by train or by bus? I haven't been able to find any information about buses in Austria, is there a webpage (like we have in Spain were we can buy any national bus ticket)?
It does not cover all the regular busses in the country but postbus.at is the main operator and does operate busses you could use. Unfortunately, it's not a part of the national train company (ÖBB) and the website therefore also includes trains, which is why busses do not show up in the search results for this particular journey…
rome2rio is another site that's very nice for intermodal comparisons, and it seems that in this case the price would be approximately the same. (You will notice that the busses suggested by rome2rio can also be found on the postbus website, but only if you look for them one-by-one).