I would like to code a traffic trading script by myself but I don't know what's the best method to identify real unique visitors...Cookies or IPs? hmm..If I use Cookies I would lose all visitors who deactivated cookies and if I use IPs I would lose visitors who come from the same network (schools, colleges,...) What's the best way to track visitors? How does google analytics track visitors?
I would suggest a concatenation of IP with some other available browser parameters such as 'Agent' etc ... doing that you'll better target individuals behind firewalls etc ..
user_agent: I think they run the same browser/os on every pc in a school. so it would be all the time same ip/same user_agent...
Maybe possible to track them with Cookies and IPs ? That need some work friend, but I think possible Maybe: If <ip is same> then <check cookies> will be better than looking to only one of them ! !