Actually this title it's not really open blocked websites, but I think this method is useful when you're behind firewall. Today when I tried to open underground websites, there are some error that inform me "The Connection has been reset"…it's mean that when my computer sends packet to the internet, the firewall read it and quarantine my link as suspicious (as written by the firewall man or the man behind firewall in their list of rules…LoL). Usually when the firewall block some URLs, you can still use ICMP(Internet Control Message Protocol) packet request or PING(Packet Internet Groper). We can still PING the target address to know it's IP Address.  

C:\Users\abcd>ping www.bbc.com Pinging www.bbc.net.uk [212.58.244.69] with 32 bytes of data:
Reply from 212.58.244.69: bytes=32 time=657ms TTL=38 Reply from 212.58.244.69: bytes=32 time=656ms TTL=38 Reply from 212.58.244.69: bytes=32 time=663ms TTL=38 Reply from 212.58.244.69: bytes=32 time=662ms TTL=38
Ping statistics for 212.58.244.69: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 656ms, Maximum = 663ms, Average = 659ms

There we can see the IP Address of bbc.com. Now you can try to copy the IP Address and then open it in your favorite browser.
NB : – This methods can be used if the firewall only blacklist the URLs and not blocked the IP Address(usually they do only write the URL, not the IP Address ). -
 This method work when the firewall didn't block the ICMP Packets. - This methods is depend on firewall configuration, so doesn't mean it will work for all website URLs that have been blocked by firewall.
by:-   @$#