Allright, before I get off the topic of coding, I'd like to breifly introduce you to the wonders of different coding languages. In the gaming world, there are four basic groups of languages:
Assembler
Assembler is to computers as English is to England. Russian is to Russia. Assembler is the closest you'll ever get to true computer language. Nice, huh? Assembler runs the fastest, operates most efficiently, and can be scaled to computers (Which makes it NOT portable, another issue with it).
However, Assembler is dead for two big reasons. First of all, it's a pain in the ass to code. Unless you intend to work with huge, unreadable files full of assembler with no real organization, you won't be working with Assembler. It's plain hard to code. No object orientation, no fun, just work. As well, Assembler has the weakness of being so old, it has a hard time doing realistic games. It may be good for games like Pitfall, but not for Doom 3.
C/C++/C#
C, C++, and C Base are the new programming languages from assembler. Easy to use, "Fun", and much more intuitive, they take Assembler to a new level. C is faster than a track runner on caffiene, C++ and C Base are not much different. There are so many tools for these great programming languages, you can almost never go wrong with them. From Half Life 2 to generic games like Theif: Deadly Shadows, everyone in the 'biz uses some variation of C.
The C codes differ in some important ways. C, the easiest to learn, is very fast but not Object Oriented, which means coding long scripts is very difficult. C++ is object oriented and fast, but is not a RAD script like C#. C# is amazing and great to use, but it can only be used on Microsoft Windows operating systems.
Still, C coding is used by everyone. You should use it too. Just do it.
Java/Javascript
There are people who like Java and would kiss Sun's ass, and there are people who hate it. I personally don't care for it. Java was Sun's smart move into the coding language by providing a pretty intuitive coding language for anything from Browser Apps to full scale applications. They run well, they run on almost any system out there, but... they can be slow.
Very slow. Slow like a snail. Unless you work like a maniac to maintain core system speed, java games can get slow, regardless if the game is in the browser or an app window. Putting it simply, Java was not made for MMORPGs (Hear that, Runescape?). I wouldn't reccomend using it unless you absolutely must. I'm not being mean to Sun or anything, Java is a great platform, just not for MMOs.
Unique scripts like UnrealScript
Unrealscript was probably one of the best moves in the gaming industry, especially in the FPS industry. Long story short, Epic games allowed developers to use the Unreal engine for games, provided they pay money and other things. Of course, UnrealScript was created to help this through. Naturally, Epic was not going to give away their blessed source code, but they gave enough away to allow people to develop high quality games with their engine.
While not necessarilly good for a MMORPG, this is probably a good option if you're looking to make a shooter game, or the like. As well, releases such as the Half Life 2 SDK allowing you to edit stuff like this is great. Still, it's a general prerequisite that you need to know SOME C++.