[nemo1618]

You could improve it significantly by implementing something similar to this: http://www.donothingfor2minutes.com/

Any mouse movement or keypresses would blank the page and you'd have to reload it to see the contents again. Of course, there are probably ways to subvert this, but it would stop most people.

[nrivadeneira]

I'm sure there are Windows and Mac equivalents, but Ubuntu has a timed screenshot option. It would be fairly easy to just set the timer, go the the website, and wait. But I agree, most people probably won't care enough or think of it.

[sirsar]

Even if there isn't one currently, windows exposes an interface to the screen through gdi+ which can be used in a C++ program, for example.

[mmvvaa]

With quicktime player, one can just create a new screen recording, and wait.

[grey-area]

Most people would just take out their camera phone and take a snapshot, as they do on snapchat. Trying to make something like this secure from screenshots is absurd.

[sloankev]

I can still print screen undetected