A: There are many tools for parents concerned about restricting access or monitoring their child's activities online.  

Microsoft Windows Vista and later versions have a tool called Parental Controls.  This allows a parent to control internet access by age rating and also creates reports for monitoring activity.  There are many 3rd party tools available as well but I'd start with the free one first to see if it works for you.  The important thing to remember is these tools can all be defeated so parents need to continue to exercise caution and talk with their kids about online safety.