Can't access certain websites in ubuntu 12.04

view full story

http://askubuntu.com – I am using 12.04. It was absolutely fine two days ago. But now all my excitement is turned into frustration. I can't open Facebook, Yahoo, Hotmail, Dailymotion and many other websites although many other websites just work fine and even I don't have any problem in downloading. My gmail account has no problem and other websites are fine. I used my network connection on other computer that had windows 8 in it and all the websites were accessible, so i think there's something wrong with my OS. My PC's date and time is correct and i dnt think its http problem.Can you please fix this. (HowTos)