Unable to load certain websites

[pwhy_3011]

I have tried to access certain websites(eg. wikispaces, hotmail etc) but it would not load. It occurs for Google Chrome, Mozilla Firefox and even Internet Explorer. It does not just occur on my desktop but on 2 other laptops as well so it shouldn't be a problem with the computer. I use the same wireless connection for all 3. Also, I have tried some solutions offered online such as pinging the website but the results are :
" Request Timed out
Request Timed out
Request Timed out
Request Timed out
ping statistics for 64.4.56.135:
packets sent= 4 recieved = 0 , lost = 4 (100% lost) "
Any help is greatly appreciated. Thanks.

[Solomon]

Have you checked that you internet is properly working? Did you try uninstalling any firewalls that you may installed on you pc and blocking some websites? Can you try winsock if that dosent work, go to start, and run there type- resetlog.txt (press enter). This way all the problems that you were facing related to browser issue will be fixed.

[pwhy_3011]

The internet is working, and I haven't done anything to the firewall. I've tried your solution as well but nothing is working.
I'm not sure if it is related but my internet has been disconnecting frequently these past few days.But I'm fairly certain that even though some websites will not load, the internet is connected because I am able to access other websites as well as load videos.