I want to make a simple game so that I can play against my friends at school. The school uses macs. Also if you can't make online games with flash what can I use. Also can they be 3-d if I eventually get good at making games?
RuneScape uses a Java applet; this is a good option for multiplayer games.
However, AdventureQuest is a Flash game and I think it's semi-multiplayer.
There seem to be some decent results, both examples and tutorials, if you do a Google search for multiplayer flash game.