1. check time and date on your computer
2. reset network configuration, make sure there are no proxy servers and you get DNS from your router not manual
3. Reset certificates database
Go to Terminal (Applications>Utilities)
sudo rm /var/db/crls/*cache.db
(you will be prompted for your password)
and reboot the computer
Yes, I can acces in all of my PC and in any browser. The problem is the imac because if I change the wi fi netwok the problem still...