My son (almost 15) has his own PC in his room. I regularly go onto the PC (in front of him - I dont sneak behind his back) - and look through the history folder etc, to see what sites he has been on. When I find "questionable" content I ask him to delete it.

The rule of thumb in the house is:

Would you listen to this music in front of your mother?
Would you tell this joke to your mother?
Would you show this picture to your mother?

If the answer is NO, then it does not belong in the house.

I also have a program which allows me to view his screen (we are networked) at any time. He knows I have it on my pc, so he knows that, at any time, I may look at what he is up to.

I dont enjoy being a policeman in my own house, but we have to take care of these children of ours until they can take care of themselves (and despite what he may THINK - at 15 my son is not ready for that responsibility!)

JMHO