While recently setting up user accounts with parental controls, I decided to test how well different websites are blocked. I was using the guest account as far as I know cannot be deleted. Review the logs after my nasty little trip through the Internet I discovered that the logs can be deleted by the parental controls menu. I found a way to do this with Terminal, but also a way, this successfully with Finder. You will only be able to do this if you have administrator rights.
The logs are stored in: /Library » Application Support » Apple » ParentalControls » Users » username. Normally, you will be allowed to see the /Users folder, but you will not have access to it. Accessing the file and deleting the log is straightforward: 
- Highlight the Users folder.
- Select Get Info from the Action button.
- When the information window opens, click on the lock in the lower right corner to authenticate.
- Click the + and add yourself to the permissions list.
- Assign yourself read/write privileges.
- Return to Finder and select the desired user.
- Entries appear to be organized by date. Delete folders covering the dates you would like to erase.
- Restore correct permissions for the Users folder.
- Restart computer.
This should completely erase the user logs as seen in Parental Controls.
where can i find the library you say to go to
i cant find it, if it in finder?