Do you have any ad-Blockers? what is your firewall? any popup blockers?
you may need to allow the website through your firewall if its not windows firewall
if you have windows Firewall then an ad blocker/popup blocker is blocking it, allow www.facebook.com through that or turn off your ad blocker/popup blocker
Q: why would an ad blocker/popup blocker block Facebook?
A: Facebook contains elements that are often identified as ads or popups, Most of the content are popups/ads, and as such since the entirety of Facebook runs off popups/ads, that is blocked as a result of being identified as unsafe, do not be surprised, some websites are blocked like this that are actually safe and are otherwise known as False Positives in terms of spyware, viruses, Potentially unsafe websites, etc
Q: Is there a solution?
A: Yes, uninstall your popup/ad blocker IF you havent bought actually bought it and download and install Peerblock:
for your reference i have mine set to block:
and if you use Google Chrome or something that uses Google Chrome Extensions, install this, it doesnt block Facebook, but blocks all ads and saves your download bandwidth, i cant recommend this extension highly enough :) :
tell us how you go