Facebook isn't working in Safari or Chrome

Not too many and meaningful details, context to work with so here goes.

1 - Restart in Safe Mode. This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts. The boot up will be slow and can take some time - Normal.

2 - Does the issue present in this mode ?

3 - Sometimes a Safe Boot followed by a Normal Boot will just put things right.

4 - If not - there could be something in the main User Account playing up. To further isolate this - Set up users, guests, and groups on Mac. Then log out of the Main User account and log into the dummy account and test again if the issue persists.

5 - If the issue is present in the dummy account - then, this appears to be a System Wide issue on the computer.

6 - If after performing each of the above steps in the order that have been presents and still have issues - please advise for possible further assistance.

Hard to tell what you are talking about with so little info. What happens when you try to go to the Facebook site? How about Firefox?