YouTube was blocked in Pakistan on 17th September 2012 by Pakistan Telecommunication Authority (PTA) which controls and maintains the internet in the country .
PTA had asked YouTube to remove the trailer of anti-Muslim movie ” Innocence of Muslims” from the website but YouTube refused to do so. Muslim community found the film insulting the Islam and mocking Mohammed. There were protest all over the country to have the videos removed from YouTube. As it was not done, it resulted in PTA blocking the website in the country.
There have been few other websites as well which have been blocked in Pakistan for a certain duration. These are namely Twitter , Flickr ,WordPress , Wikipedia.Even Facebook was blocked in 2010 after a Facebook page was created to submit drawings of prophet Mohammed. Although the ban was lifted two weeks later.