I just installed ubuntu on my laptop. I can't ping or open a site with it's name but everything works fine when i use IP address. I already tested a few ways like disabling ipv6, changing dns server and changing some configuration in firefox.
it is an error in DNS server settings. DNS is service translating domain names to the IP addresses. Your DNS server is not set properly or does not work properly. Usually this can happen if you set fixed IP address with incorrect DNS. The advice in comment to setup DNS to 184.108.40.206 is correct and can help you, but better will be, if you use your local DNS, usually it is given from your provider or it can be IP address of your local router. For most cases to setup DHCP (automatic IP setup) will work.