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When someone tells you a hilarious joke, you're likely to respond by slapping your thigh, throwing your head back, and chortling with abandon. Should you discover that same joke in your e-mail in-box, however, you're likely to respond with LOL, LMAO, ROTFL, or in the event of extreme mirth, by ROTFLMAO.

If you're new to chat rooms, instant messaging, or e-mail, the above acronyms may seem vaguely official or even intimidating. Relax. Those particular alphabet-soup concoctions simply mean laughing out loud (LOL), rolling on the floor laughing (ROTFL), and laughing my, er, ankles off (LMAO). They're just a few examples of the everyday cyberspace shorthand used to convey laughter and anger, approval and disapproval, love and hate--and everything in between--with a few quick keystrokes.

In addition to acronyms, cyberspace slang also consists of an almost endless assortment of emoticons. An emoticon is a combination of letters, symbols, or numbers that paint a picture (often when viewed sideways). For instance, :) is one of the most popular emoticons, used to represent a smiley face. If :) still doesn't make sense, tilt your head to the left.

Acronyms and emoticons have become the hieroglyphics of a hurried generation. They're informal, often clever, and they save time. But they aren't always appropriate. For instance, sprinkling emoticons throughout a message to a potential employer isn't a good idea--unless the employer is an 18-year-old chat-room habitué. And like any slang, the use of acronyms and emoticons can make those who don't know them feel excluded. So always be considerate about where you use Internet shorthand--and how often.

The following glossary will help you decipher the most commonly used acronyms and emoticons. Plus, we've thrown in a few favorite, exotic examples of each. And because we just couldn't stop ourselves, we've come up with a few pop-culture-inspired acronyms we'd like to see. The possibilities are endless, but if you use your own home-grown acronyms or emoticons, don't forget to explain them to your readers.