I had no issues accessing the facebook site. Since you mentioned you could not access from other browsers as well, did you check if your firewall in case you are under one or your Internet provider is blocking it?

One solution you may want to try is given in this thread, as experience by another user in the past: https://support.mozilla.org/en-US/questions/1146492

Any improvements?

Your suggestions did not cure my problem. My firewall is handled by Norton 360. I went thru any settings there that I thought might be the culprit and deactivated them. Restarted Firefox with no change. BTW if it didn't show up, I am running Windows 10. A couple of my friends are using the same internet provider (Cox Communications) with no problem accessing Facebook. I've even checked some settings within Windows with no change. Where do I go from here?

Ignore my last message. I tried something "old". The phrase - "When all else fails, reboot". I did, and it now works in all browses. I apologize for bothering you. But thank you for trying to help. Les