Unable to access Facebook from ANY browser on my Mac (suddenly)

I have the same problem

Exactly which problem do you have? It would be better to start your own thread.

i dont know how to change the DNS server

You can change it in your Mac's network preferences even if you can't change it in your modem/router.

when i try to clear the DNS cache in terminal it never say i actually did it

This is normal.

I pinged facebook.com and it worked, but http://www.facebook.com/help didnt, nor did https://www.facebook.com or http://www.facebook.com.

Are you saying that these don't work with a web browser? They all work for me.

I did start my own thread, but was also trying to figure it out by looking around.. I have a 2009 macbook and im on mountain lion. i usually use chrome, but also have safari and firefox. about a month ago i started having problems with facebook apps (simcity social) and then i was unable to get on to facebook at all. from any browser. ive restarted my router and computer numerous time. cleared the cache and tried a few of the suggestions listed on the forums but nothing as worked. orginally i was only unable to get on facebook when i was at home, but i would bring my laptop to work and it would be fine. but today it wasnt connecting again. every other website works. any suggestions?

If I understand you correctly you cannot access a particular web site from a particular computer in two different locations.

This appears to be a Facebook and not a Mac issue but you could try:

1 - Other web browsers

2 - Reset Safari with all boxes ticked

3 - Other accounts on your Mac

4 - Other computers.

The issue may be with your Facebook account (I don't have one). Data for this may be stored in cookies, other local storage or on the Facebook site.

Until this is resolved you should regularly reboot your Mac.

i've tried all browsers and ive used my roommates mac and it worked fine on the same connection. it is def. something with my settings on this computer.

What happens with items 2 & 3 in my earlier post?

I had the same problem, and I just fixed it. See this thread-https://discussions.apple.com/thread/4612888?start=0&tstart=0

Let me know if this works!

Andrew, thanks for your post. Restoring an old hosts file fixed my problem. My question now is how did the hosts file became corrupt or modified which blocked my access to facebook. Anyhow, I was about to pull my hair out. Thanks so much for posting.

One of the difficulties with this thread is that it has been taken over by people who think they have the same problem as the OP.

In your case you said that the issue did not affect your guest account. The hosts file resides at /etc/hosts and affects all accounts. I am unable to explain how a hosts file could affect some accounts but not others.

Not much modern software modifies hosts files. At one time it was a popular way to block adverts. Installing an ad or some other blocking application or plug-in could modify the hosts file. This can be a problem if something is blocked which causes pages to stop loading.

Like any piece of software a hosts file could be affected by random corruption. Not very common but can be caused by power outages, forced shutdowns, forced quits, imperfect RAM or disk problems etc.

Yes, the part about it working as Guest login really threw me. Apparently the hosts file does not affect the Guest. It affected every user I created, Standar or Admin, just not the Guest. I tried "everything" prior to restoring an old Hosts file from backup. Given that it was just the Facebook site that was affected from the so called corruption, I'm assuming it was some type of malicious ware. Anyone come across this?

I may test the guest/host connection on my OS later.

Anyone come across this?

Yes, particularly with large US software concerns. It is common for them to work with other sites for ads and web traffic analysis etc. They often fail to load if these third party sites are blocked. I recently added a frequently used long list of sites to block to my host file and had to remove a few items.

Who or what edited your hosts file?

According to my tests my PPC Leopard hosts file affects all accounts including the guest account.

My view is that either you are mistaken or there is something strange happening on your Mac.