[ubuntu] problems loading social network

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http://ubuntuforums.org – hello to everyone, I am new to Ubuntu and I'm trying to learn how everything works here... I ran into a problem and I cannot solve it... I have search without success. My problem is that when I want to open vkontake (a popular social network site in Russia and the CIS countries) a message appears saying "Oops! Google Chrome could not find vk.com" or "Server not found, Firefox can't find the server at www.vk.com. It does not matter what explorer I use. I know the site works because if I change to windows the page opens with out any problem. I really need help, I am try (Hardware)