Can not access certain websites from my MacBook or iPhone [WiFi]
Ping (ICMP) packets can be blocked though you are still able to access the website.

Telnet to port 80 is actually a better test to verify whether you are able to connect or not.

Over here connecting to http://ilpost.it results in no problem:

$ telnet ilpost.it 80                                                                   (28-09-12 13:58)
Trying 151.1.175.113...
Connected to ilpost.it.


Although ilpost.it redirects to http://www.ilpost.it/