RealtimeMultiplayerNodeJS is a framework specifically for building HTML5 multiplayer games with the Client / Server model. In this model, connected users send only input and the game itself runs on the server.
Clients are interpolate between two known world snapshots based on the current synchronized time.
(Like a DVR)
This is the Box2D demo that comes with RealtimeMultiplayerNodeJS.
(Song is Little Fugue in G Minor - 8bc.org/music/Minus+5/Little+Fugue+in+G+minor/ )