I would like to suggest you to use idevaffiliate software. It uses cookies and once people click your affiliate link, it will then transfered to either your main page or any customized link. I just don't like any affiliate system that used the 'replicated' concept where people can see clearly that the link is an affiliate link. I hate that, because people will then delete the affiliate id and refresh the page. The commission will then go directly to the admin, not the affiliate.