Monitoring Software Teenager Related Troubles

My son spends hours sitting if front of his PC (My Space, Facebook and other things). I am looking for a software that lets me monitor what he is writing and reading in all of these web sites. I have seen a few on-line, but I am not sure which ones are really trustworthy and reliable. I would like to go into his Facebook page but I don’t know his password… Could anyone help me out in recommending me a good comprehensive “computer monitoring software” so I can feel more relieve? I thank everyone who responds to me in advance for your help and time!

Thanks so much!

Julian