While OPENDNS may work I'll let you find out how. Facebook is one of the more popular blocks implemented on OPENDNS.
The other solution is to block it on the machine. Use the HOSTS file to do that. Since that is widely documented, I'll let you research that further.
But the aproach you are taking does not appear to be one this router will support.
I'm using a D-Link DIR-825
and trying to block access to certain websites from one computer on the network.
The computer is a laptop and does not have a designated IP so I was trying to use the machine ID (hardware address).
I tried the following from the router setup pages:
DENY computers access to only these sites (popup menu choice)
Machine: (hardware address of laptop (from Network Settings))
Filtering: Block Some Access
I've verifeid that the hardware address of the laptop remains constant and also double checked that it is entered correctly.
What am I doing wrong because the laptop is still able to access those sites?