How to block unwanted websites
You can try using something like parental control software like: cyber patrol parental control, Parental control bar, Safe Families We-Blocker Parental Control.
if you are browser specific and using internet explorer then you can use content advisor. This shows up in internet options and if you want to use some type of software to block sites according to category then the best option is k9 web protection.
Try to Open DNS besides filtering of sites based on your preferences it also blocks malware sites.
By using Windows Firewall applications you can be block for the users from that particular PC but no internet website. You can yourself check also go to Control Panel then go to Windows Firewall go to Exceptions and there you will find only the services that can be blocked. If you try to add new ones by clicking Add Programs right applications can be blocked for the users from that particular PC but no internet website.
The most easy and secure process to block particular websites on your client operating system is to use d windows HOST file. The steps are
go to C:\WINDOWS\system32\drivers\etc
find a file named hosts.
Open it with notepad then go to the end of d file and in a new line write particular sites full name or url.