They should have a policy on this and will help you get it taken care of proper.
In the meantime why is your machine not password protected to safeguard not only you but your company's "goods."
"I can't just log the computer off when I'm not around."
-> But you can have the screensaver kick in and password that.
Bob
Turns out that on days when I'm not at work, a co-worker is using my computer to access two specific porn sites. I would just like to block those sites to see if he gets the hint before reporting the problem. I can't just log the computer off when I'm not around.
**Bonus Challenge: Can I redirect him to, say, a page on my own domain that will let him know that he is busted?
These are my specifications:
OS: 10.4
Browser: Safari
Connection: DSL
Network: Hard-wired ethernet, connected to network printer but not to any other computers on the network.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic