Your The Man Now Dog (YTMND) is, as the site creator says, a "site created for the purpose of furthering the creativity of its users. It stems from an idea that, using sound, and image, and some text, the users can convey a point, funny, political, or otherwise, to the general media."
YTMND began in 2001 as a single website called yourthemannowdog.com, which consisted of a tiled image of Sean Connery from the movie Finding Forrester, looping audio of Sean Connery saying "You're the man now, dog", and text of the quote over the image. After the popularity of this website, the designer eventually came to create what we know as YTMND.com, which has become an increasingly hot site on the internet because of its diverse content and the ease by which anyone can participate and create one's own YTMND.
A YTMND must constructed by following specific guidelines, which include: 1) You can only use one image (stretched, centered, or tiled) that exists in either JPEG, GIF, or PNG format. 2) You can use only one sound clip. It must be either an MP3 or WAV file. 3) You can use up to three lines of text and the font never changes.
Although these guidelines limit what you can create, the creativity arises out of how a user can manipulate an image, a sound clip, and text into something interesting. Like any medium, there are rules and limitations that define the content within that medium. Comic books, Films, literature, etc... all have become distinct media because of the grammar that defines them.