On Twitter and some instant-messaging services, there is a limit to the number of characters a message can carry – however, Twitter now shortens links automatically using its own URL shortening service, so there is no need to use a separate URL shortening service just to shorten URLs in a tweet. I have used Google Analytics, bitly, ConversionFly, and ClickMagick works the best for me. See if you are using Classic Analytics (ga.js) or Universal Analytics (analytics.js).