LOL

According to Haig, M. (2001) and Franzini, L.R. (2002), LOL is an abbreviation for laughing out loud, or laugh out loud (Egan, M, 2002), is a common element of Internet slang. It was used historically on Usenet but is now widespread in other forms of computer-mediated communication, and even face-to-face communication. It is one of much initializes for expressing bodily reactions, in particular laughter.

References:

1. Matt Haig (2001). E-Mail Essentials: How to Make the Most of E-Communications. p. 89. 

2. Louis R. Franzini (2002). Kids Who Laugh: How to Develop Your Child's Sense of Humor. Square One Publishers, Inc. pp. 145–146. 
3. Michael Egan (2004). Email Etiquette. Cool Publications Ltd. pp. 32, 57–58. 

Original source: from Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/LOL%20(18 April 2012)