There is no server side OS available yet.
It is not impossible to code on server side using javascript as there are frameworks available today which lets use of javascript on server side. But usage of this is not that high as most people prefer the normal way of using AJAX if they want javascript to interact with a server side language.
You can't. Sessions are a server-side technology. To properly implement a session, you have to use a server-side language like PHP, ASP, or Ruby.
yes just put the world file that you want into the world folder in the server files
Google motsly uses Python.
Many possibility. C is one of them.
bgp is the largest protocol
Processing that is done on the client computer instead of the server computer. Most online multi-player games use client side processing to reduce server load and performance.
Processing that is done on the client computer instead of the server computer. Most online multi-player games use client side processing to reduce server load and performance.
the world wide web is long for www there is no private server for the world web it just is free for everyone to use but it contains plenty of viruses
Yes, JavaScript was (and is) used server-side. In 1994, Netscape released their Netscape Enterprise Server, which allowed for the use of JavaScript as a server-side language. It was never really hugely popular. But Apache still makes available their "mod_js" for this express purpose. (Even if it's not intended as production use, rather described as "just a toy.")
HTML is client side scripting so the Form will have to be in HTML (unless you use something like Flash or Java) and the submission will require a Server side language in order to do anything with the code. So to answer your question, you do not have to use HTML; you do not have to use PHP.However you will have to use a Client Side Scripting language like HTML and a Server side scripting language like PHP.
Each server as its own set of commands. There is not a list of all commands available as they are different from server to server. If you want to know the commands you can use on a single player world, just use /help you the list.