Content Scramble System
Content Scramble System is "the other CSS"; unlike Cascading Style Sheets, which help make Web sites more attractive and adaptable, this CSS helps make DVDs less usable and adaptable, by imposing encrypted protection to attempt to prevent the use of their content anywhere the content owners would prefer it not be used, such as in players for open-source operating systems, or user-friendly devices letting their users get around non-skippable ads or play discs outside the country they were released.
CSS was introduced in 1996, and in 1999 the unauthorized CSS decrypting program DeCSS was released by "hackers", raising the question, "What took the hackers so long?" DeCSS provoked a large flurry of legal cases, the end result of which being the complete suppression of the program to make it absolutely impossible to find subsequently... only kidding; it has been all over the Internet ever since its creation, regardless of its legal status. The essential parts of its code (including the encryption key) are compact enough to fit on a T-shirt, and in fact, T-shirts and other merchandise containing it were actually made.