Thx I decided to start with C# and Unity for web, C# with XNA for windows and Java for cross-platform including web, but I will start with C# because is easyer to learn. But in the end I will end un with C++/C#/Java, C# and Java being the main focus.Your advice is very good and valuable, but just to nitpick slightly (We're on the internet after all ), you didn't answer this question fully, but he has the impression that you did, so he's walking away with faulty information.
C++: Very scalable. It's arguably the fastest object-oriented language, or among the top.
How scalable is C++ when it comes to web games?
Question: "How scalable is C++ when it comes to web games?"
C++ is not made for web-based games, and if you want to get C++ games working in someone's web browser, you have to do weird stuff like having users download custom or uncommon plugins for their browsers just to play your game, presenting major security risks and driving away users, whereas some other languages (like Java) most of your userbase will already have the plugin installed.
C++ is not the ideal language for web games. Neither is C#, though C# is somewhat better (Unity plugin, and I don't know what else, but it seems Microsoft designed C# for web support as well). Python I don't have a clue about, though I imagine it's in the same boat as C#.
Java is much better suited for web games, at least presently.
"I was thinking he'd use C++/C#/Java/Python for the backend (or what runs on the server) and the weblanguage for the frontend (or what runs on the client)."