For a home or small network, if you have a broadband router such as Linksys or DLink, there should be an option that allows you to enter the addresses of sites you want to be blocked. Depending on the size of your network, you may want to consider a content-filtering proxy. This will also give you the ability to block websites. Many proxies will give you the ability to access only allowed sites. This may be the method you want to employ.
For a small number of computers you can edit the host file (Windows). Add the site and set the IP address to 127.0.0.1. This method can be time consuming unless you deploy the host file from a central location/file. If you are running your own internal DNS server that forwards requests to other DNS servers you can employ this technique.
Create a forward lookup zone for the site you want to block. Example: badsite.com
Create a host record for the site.
Set the record's IP address to 127.0.0.1
Make sure you deleted the CACHED zone for the site you want to block.
This technique also works well with other unwanted hosts such as messengers, ftp sites and P2P hosts.
Another way, if you are in a Workgroup and don't have to contact your
DNS server for accessing local network resources then you can try
Opendns which is free. Available here: http://www.opendns.com/
You can purchase the enterprise version as well.
Another good rated free product is Untangle which does the decent job of firewall and security in a small size networks.
http://www.untangle.com/
Internet Explorer also have a nice way to control website access. Go to the Internet Options > Content > Content adviser > Enable. One new box will open and inside that go to General > Create Password. Give some password which you want.
Now when you try to open any website it will ask for the password.
If the requirement is such that you do not want to block the internet completely,
open the website which you want to open all the time and when it will ask for the password then give the password and remember to click the option i.e always allow to view the website. After that it will not ask for the password at any time you want to open that particular website, but if you try to open some other site then it will ask for the password.
Like this the websites you want to open, just give the password and also tick mark the option i.e always allowed that website to view.
