Twitter cards make it possible for you to attach media experiences to Tweets that link to your content. Simply add a few lines of HTML to your webpages, and users who Tweet links to your content will have a "card" added...
Today's been a bit frustrating - technical bugs with a website wiped out the best part of the day, but the internet's full of funny things. Funny, in the "lol" sense of the word that is. Here's 4.