The chances are the URL for Facebook (www.facebook.com
) is blocked, so you cant visit www.facebook.com
or any page in that directory i.e. www.facebook.com/pages/profile
. But in the case of Facebook Blog, the URL isn't www.facebook.com
it's actually blog.facebook.com, it's what's called a subdomain when they put a word in front of the root domain and it becomes a new domain. blog.facebook.com isn't blocked on your systems yet
and so you can still access it, you might also be able to access other subdomains of facebook.com such as apps.facebook.com as well.
Hope this helps.