Linux Whitelisting websites in linux

I want to create a whitelist to determine which sites a person can go to on a specific linux workstation.

I'll be using Ubuntu, but I imagine this type of solution should be fairly distribution independent.

I want the list to have something like:
http://www.example.com/foo/
http://demo.com/
http://foo.bar.com/

Which would allow me to view:
http://www.example.com/foo/bar/baz.htm
but not
http://www.example.com/index.htm

and http://www.demo.com/foo/bar.htm or http://test.demo.com/foo/bar.htm
and http://foo.bar.com but not http://www.bar.com

make sense?