No registration required. 1) Open bug URL. 2) Select departure and destination (e.g. Milano->Venezia), click Go. 3) Click shopping cart icon for one of the options (at the right). 4) From the first popup (Fare), select "Standard" (below "Choose your rate" and "Flexi", might depend on train type). Results: the page reloads, "Choose your rate" option disappears, the rate gets changed to "Flexi", price field for 1st class gets filled with garbage, 2nd class price remains empty. Expected results: the page reloads, "Choose your rate" option disappears, the rate remains at "Standard", "Adults" popup value changes to 1, both 1st and 2nd class prices are set to sensible values. These are ToT results; in shipping Safari choosing a rate doesn't cause any action, so the site is inoperable, too. Works correctly in Firefox.
This sounds like what was happening with Bug 13197 before the USPS site apparently changed.
The issue described above was fixed in bug 13278, but some problems still remain. Here is one reproducible sequence I could find: 1) Set the fare to Familia 15%. 2) Set the number of adults to 4. 3) Set the number of children to 4 (an alert appears, and the number gets reset to 1). 4) Set the fare to Familia 25%. Results: an alert appears, the fare is reset to Flexi. Expected results (Firefox): the fare is set successfully, but the number of adults is reset to 2. I also saw several glitches that I couldn't reproduce. Sometimes, the first fare (Flexi) disappeared. Other times, popups for the number of travelers got additional "0" options inserted at the top.
Filed bug 13287 for the second issue.
All known issues with this site are fixed - and it also got redesigned in the meanwhile.