I'll bet that amidst the talk these days of being green, and the environment that users of the internet don't consider that servers hum away in data centres 24 hours a day, emitting carbon into the atmosphere.
Would you consider that 18.5mg of carbon dioxide is emitted per second of client interaction a website ( US data).
and... to get you thinking even more deeply how about these statistics:
Watch this 3 minute video, it'll get you thinking
Source: Institute for sustainable development