1. A computer system configured to provide an online media exchange, the computer system comprising: a web server configured to provide a user interface to advertisers and publishers accessing the online media exchange; one or more application servers configured to: manage data objects associated with respective advertisers and publishers and further configured to manage online negotiations between advertisers and publishers regarding placement of advertiser ads on publisher websites; and automatically match advertiser offers to publishers and rank the advertiser offers, wherein the one or more application servers are further configured to match the advertiser offers based on: an effective cost-per-thousand impressions (ECPM), an intended ECPM, conversion rates, and return-on-investment calculations; and to rank the advertiser offers based on the matching; a database in communication with the one or more application servers, the database storing data including the data objects; and one or more ad servers in communication with the database, the one or more ad servers configured to automatically serve data defining advertiser ads that match a contracting publisher's websites, to an end-user when the end-user navigates to the publisher's websites.