If you need to shrink a longer URL while composing a tweet please type the URL into your tweet (ex: http://www.tweetcaster.com) and then click on the shrink URL (chain link) icon located under your tweet and to the left of the attachment icon. If this icon is grayed out then the link has not been entered correctly and will not be able to shrink – make sure you have included http:// in your URL so that the link is recognized.