on the net, especialy in chat rooms, you may see abreviations of common expressions like lol (laughing out loud) or brb (be right back). Here's a list of some that i know:
Lol-laughing out loud
Brb-be right back
fyi-for you information
cya-see ya
ttfn-ta ta for now
noyb-none of you buisness
itc-it's the coolest
bfn-bye for now
wysiwyg-what you see is what you get
gtg-got to go
ne way-anyway
k-ok
oic-oh i see