A virtual private network (VPN) is a secure way of connecting normally to another local network over the insecure Internet but can be used to surf in the web too. You need a VPN-Provider. Now think – if your VPN-Provider is free, then he is selling you. That means he is using your data for adds and looking what you are doing. This is not secure.
A VPN-Provider with a limited free contingent is CyberGhost: http://cyberghostvpn.com/en/surf-anonym.html
A very good secure non free VPN-Provider is Perfect Privacy: http://perfect-privacy.com