Well, Pakistan government has a history of blocking many websites inside its country on the name of National Security or due to blasphemy or inflammatory content. Websites like Facebook, Twitter, Youtube, Wikipedia, Flickr, IMDb have an history of getting banned for a temporary period of time.
This time PTA (Pakistan Telcommuncation Authority) has banned WordPress. WordPress is a blogging platform that hosts millions of blogs all across world.
Users trying to access WordPress are seeing the above message. This ban is currently affecting the official WordPress blogs and blogs which are hosted by WordPress only, but the self hosted blogs are safe and accessible.
It has been stated that this block is related to National Security and somewhat related to Pakistan Day (March 23) will be applicable for two days from now.