fbcdn.net

[tammyinmo]

This link is used to open facebook and should be listed as social networking but it has been denied in that area by someone,

[mattwilson9090]

Yes, the domain is categorized as a content delivery network and not social networking. That happened in October of 2013. If you disagree with it you can flag it for review or file a support ticket, but it appears to be the correct categorization as it does appear to be some form of CDN that redirects to the facebook.com domain. I'm not sure of how everything is setup for it to function, but if facebook.com is blacklisted, or the domains that it belongs to are blocked then facebook should continue to be blocked. The same should apply if you are trying to whitelist facebook rather than blocking it.

[discloser]

"This link is used to open facebook"

This is not a link, but a domain name, and no, it is not "used to open facebook".  It is used for CDNs by Facebook.  If you attempt to visit fbcdn.net, you're web-hopped to https://www.facebook.com/?_rdr which should be blocked if you have Social Networking selected as mattwilson9090 said.  So no need to tag it as Social Networking.