Have you ever sat through a seemingly endless parade of  previews at your local cineplex waiting to see the film you just paid for, only to wonder if the ones that are coming out in the next few months  are really  as good (or bad) as they seem to be? Since their first appearance in 1912 after a Thomas Edison serial called What Happened to Mary, trailers - so called because they originally came after the film - have grown into one of the most popular advertising medium in the world. And even though some moviegoers love them, and some hate them, the one thing you can be sure of is that a great trailer doesn't always translate into a great film. Recently, the Independent Film Channel published its list of The 50 Greatest Trailers of All Time. Check it out and see what you think.