Tribune Company plans to have users of its various newspaper websites sign in with a “universal registration” that is designed to make it easier for advertisers to target users. Don Meek, president of Tribune365, the company’s national sales unit, mentioned the plan to AdAge as an example of why its reluctant to charge readers for online access. The registration system is expected to be rolled out across all Tribune sites this year; a system for Tribune’s mobile sites is planned for next year. Tribune isn’t saying exactly what the registration will entail. The goal however is pretty clear, as Meek told AdAge that Tribune wants to promise the ability to target ads down to specific household addresses.