> If you've been working on a mainframe and your employer decides to retire it but is happy to put you on some front-end web stuff which you've never touched, that's probably going to be a tough adjustment that may not end well.

Sure nice of them to give you that chance rather than just laying you off though. Would be even nicer if they spent a little money to train you on the front-end web stuff. Employers used to do that sort of the thing all the time - retrain known good workers rather than just fire them and hire new (unknown) ones.