How to stop people printing out web pages (or at least make it a giant pain to)

Terence Eden reminds us that CSS—the basic, nothin'-fancy code used to style websites—has simple commands that prevents printing of websites using the normal print controls. You'd need to do something tiresome like edit the CSS with developer tools or screengrab pages to get the job done.

I've tested this, and it works in Firefox, Safari, and Chrome. It's trivial to defeat this technical protection mechanism if you're handy with developer tools – but I guess those aren't the people who are printing off the entire Internet.

Fun tricks. Instead of using CSS (or javascript for that matter) to hide stuff, use it to show/insert stuff the person printing (or copying) the document won't realise is there unless they closely inspect the document/paste afterwards. "Perhaps I am a plagiarist" for example, or "Leaked from the workstation at"