In recent past, Facebook banned in Pakistan and then YouTube and Twitter also blocked. People can’s access these sites in Pakistan as message appears that “You are not authorized to access this page”. But if your country, college, office, school is blocking any site and you want to access that from there, you can also use Proxy Servers to do the same. Here is the list of 10 Proxy websites which are nothing but 10 ways to access blocked sites at your place.
Update: Egypt bans Twitter, read how to access twitter in Egypt
To use these proxy sites, you just need to paste the URL of the blocked site in the input box and then you will be redirected to a page where you can see the data from blocked site. Some of these services are free to use but some of them are paid as well.