I had this same error while logging on to my University's wireless internet. I contacted both apple and my university help desk and here's the steps I followed:
Go to Settings -> General -> Reset -> Reset Network Settings
Then go to back to Settings -> Wifi and select "Other"
Manually type in name of the wireless access point you wish to connect to, even if it displays under "Choose a network" (which it should)
Once it connects, go back into safari and try to load the page - should work fine.
I really hope that helps!!