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Creating viral videos and concepts has become a keystone for many businesses marketing online.

Such Web phenomena are known by technophiles as "memes." Coined by biologist Richard Dawkins in his 1976 book "The Selfish Gene," a meme is a unit of cultural information -- an idea, a practice, a phrase, or an online video --that's passed on virally. Although sometimes frivolous, every word-of-mouth marketer dreams of creating memorable memes that will catapult their product or client to fame.

Over the last few years, 4chan.org has become one of the most talked-about sites when it comes to launching new memes. After appearing on the site, "LOLcats," humorous images of cats with loud text beneath them in a fake language called "LOLspeak", stormed the Web last year. (For example, instead of saying "hello," the cats would say "oh hai.") Another phrase "So I herd u like mudkips," a reference to a sea creature from the popular animated show "Pokémon," spawned thousands of tribute videos on YouTube. 4chan.org began as a simple message board with pictures and text. It was started by Christopher Poole in his Long Island bedroom in 2003 when he was 15 years old. Since then it has grown to more than 3 million monthly users, according to Mr. Poole.

One of the site's most popular memes is an online bait-and-switch known as the "Rick Roll." Here's how it works: A friend sends an email suggesting you take a peek at an "amazing" online video and passes along the link. You follow the link, but instead of the video you expect, you've been sent to the music video of Rick Astley's "Never Gonna Give You Up," a hit song from 1988. Over the past year, Rick Rolling has become an online sensation, pushing Mr. Astley's video past 16 million views on YouTube.