Here's less than 140 characters for ya: trivial texts or not, every one's all a-twitter about tweeting. Twitter operates a free Web site that blends social networking with the ability to post short messages (or micro-blogs) limited to 140 characters or less, commonly known by users as "tweets." Tweets are designed to be accessed on mobile devices and through the Internet, where they are posted to a personal Web page that can be restricted to select viewers, or viewed by anyone. Unlike instant messaging, viewers do not reply to Twitter postings. CEO Evan Williams, Jack Dorsey, and Biz Stone co-founded Twitter in 2006. Initially designed for use on personal computers, Twitter launched a mobile interface in 2007.