Networking – I can Ping facebook but browser keep showing time out error

it's been more than 4 weeks now that facebook occasionally go down for me, it start by saying that it can't connect to chat, then when i reload the page it tells me that i don't have internet, but i do, every other website works perfectly, i tried using almost all the available browsers, i also tried on other PC and even tried on a Macbook but still the same issue.

When i try "Ping www.facebook.com" on command prompt (win7) it works and most of the time when i type the facebook Ip on the browser it works either.

here is the things i tried so far to solve this problem !

• restart the router

• clear browser cookies/cache and remove all extensions except the very
  basics one

• Ipconfig /renew

• Ipconfig /release (it took time more than it needed so i canceled it
  )

Remark
I can access facebook.com at any time using a proxy server from website like proxy4free.com, but it's annoying and facebook keep blocking my account and asking for new permission everytime i do that.

One last information, 99% of the time am using my laptop and connecting without a cable but i also tried using cable and there is no difference at all.

Thank you