The interface is the environment in which people work and play on the web. It is the arbiter of all the communication and interaction that takes place there. If there is an action available in an interface, then you can perform the action. If an action is not available in an interface, then you’re out of luck. While we are intuitively aware of this, just as we are aware of the weather, we rarely reflect on how much our behaviour is determined by the interfaces we use. Almost all of it!