What does HTTP Error 403.6 means?

Hi,
I was browsing my Facebook when I saw a link of a funny video and I clicked it. My page went blank and displayed the message, "HTTP Error 403.6". I closed Internet Explorer, refreshed my page and tried to access my Facebook again. Sadly, I cannot log-in anymore.
Facebook page doesn't load anymore. I tried to research about this problem and I saw this one note saying:
"HTTP Error 403.6" Error Message Occurs When You Try to Access Web Sites Beyond Proxy Server
What exactly does this mean, I have no idea.
Thanks.
