Sometimes a problem can not be the opening of a website not only because the internet connection is fine, could have been from a DNS Server that is used will also be influential. Because the DNS server task is to translate domain names into IP addresses that can be understood by the computer, if there's any errors of course those sites will not be found.
Therefore you are in addition to test your internet connection by pinging it's good well you try using the nslookup command. In fact how the IP address of the website that are notified by the DNS server you use. How to use it is to invoke the command prompt (for windows, can be also with linux terminal), type the domain name followed by the nslookup command and then press ENTER. An example is the nslookup kenzierider.com.
You'll get what information the server DNS name and Ip, as well as any IP address (can be more than one) of the website that you check with nslookup. If at the time you do some checking occurs "DNS request time out" then the cause of the problem could be your internet connection due to instability of the ISP that you use or indeed the DNS server you are using is also problematic.
The solution to the first problem is to contact the customer service of your internet service provider, is the second you could replace the DNS servers that are used to Google DNS or OpenDNS. Good luck.