An ad broker is a middleman between advertisers and publishers. These are individuals or media agencies who make their living by finding and negotiating ad spots for advertisers they represent for a fee or percentage of sales from both advertisers and publishers. Ad networks can be referred to as ad brokers as well.
Double Opt-In
Double opt-in is a signup method that includes two steps: giving contact information and confirming the will to be subscribed by clicking a link sent