You can block any website which you feel could be bad for any of your family members or any other person who uses your computer. This can be done by altering the host file. Here is the location of host file.
C: >> Windows >> System32 >> drivers >> etc >> hosts
Click on this file to open it. If it asks which program to use for opening it then choose notepad. At the bottom of this file there would be few or at least one ip address like this:
Just add the website that you want to block as shown. For example you want to block http://www.facebook.com/ then it should look like this:
Now close the notepad and click save. Just check www.facebook.com and you will see its blocked. In a way you can add any number of websites that you want to block.