I hope that Khan Academy will in the future begin teaching some of those languages, but currently they are not in the plans, I don't think.

I don't think so. One of the reasons HTML/CSS/JS is used is because they are client side web programming languages. Python and C# When used in webpages are better as server side languages. And C++ Is rarely used to create webpages except for performance critical webpages, Because it is pretty low level and hard to use.

If you want to learn those languages, There are plenty of great tutorials on the internet and some of them are interactive.

Yeah, that's true. One website you can visit is codeacademy.org.

@Legolas: Yeah, codecademy.org is a nice site! Although they don't teach C# or C++ there. They do have a python course though!

I know how to code in C++ and it is really fun!!

I recommend it!!

C# is also fun

I use sololearn.com

There teach like 20 programing languages

Same question.