Seen whilst browsing ESPN.com comments section using the ELinks console web browser:
You are using an incompatible web browser.
Sorry, we’re not cool enough to support your browser. Please keep it real with one of the following browsers:
- Mozilla Firefox
- Safari
- Microsoft Internet Explorer
Hah! :D
Of course, since this page consists of text-based comments on a blog entry, the argument could be made that the Facebook-powered webpage is the incompatible element of this equation…but let’s not split hairs. ;D

I have struggled with this one for a long time, tried dozens of things that were suggested by others, and finally cracked it this morning! I have Symantec Endpoint Protection installed. I had to go to Network Threat Protection -> Options -> Change Settings and under Stealth Settings, remove checks from all 3 boxes.
What’s important is that this seems to be a case of your firewall, whatever kind you are running, trying to protect you from some transaction that is required by Facebook, so if you have a different firewall than Symantec Endpoint, look for some setting that might be filtering out what Facebook needs.
It is unfortunate that Facebook gives this very misleading error message under these conditions! Symantec, at least, does warn you in the Settings box that enabling these settings may interfere with using some websites.