Much more information required.
Are you getting this message only when trying to access particular websites, this one perhaps?
How are you connecting to the internet? Are you on Wi-Fi? Data through phone, Mi-fi device etc?
If data, which mobile provider and package - are you using a local SIM or relying on EU roaming?
If Wi-Fi have you tried a different hotspot? (FON, campsite, McDonald's, supermarket etc)
Do you get the same message using a different browser?
Do you get the same message using a different device? (try on your phone, laptop etc)