Clickthrough Rate. Slightly inexact because some clicks “get lost” between the click and your server. Also be sure to ask if the CTR is unique, meaning that each individual user is only counted once no matter how many times they click on a link.

Building a Highly-targeted Opt in List: When Money Lies Beneath the Lists
Are you successful with your Internet business? Better yet, do you think you are successful with your online business? When most online entrepreneurs are asked with these questions, they often brush it off.