AFK - This is easy: Away From Keyboard.
BAK - The companion to BRB (see below), this is Back At Keyboard. I tend to just write "back" when I return.
BBS - Though still in use as the acronym for Bulletin Board System, most chatters use it for Be Back Soon.
BRB - One of the most popular acronyms in cyberspace, BRB stands for Be Right Back.
BBIAB - Similar to BRB, this means Be Back In A Bit. Similarly, there's BBIAF, which is Be Back In A Few and BBIAS, which is Be Back In A Sec.
c-ya - A quick'n'easy way to say "seeya".
hb - Say this to someone who's going away. It means Hurry Back!
re - This isn't an acronym, but it's short for re-hi, a derivative of re-hello, both of which were commonly used eons ago on the online system chats, such as CompuServe. Basically, it's used to welcome people back to the room/channel. Note that people will also add more "e"s to the end, so expect people to say reeeeeeeeeee, too.
WB - Quite simply, it means Welcome Back.Emotional Responses
LOL - One of my personal pet-peeves, LOL is Laughing Out Loud. I don't know why it bothers me, but I just usually stick to typing out <laugh> or doing /me laughs. (which, in IRC, will show up as * juliebug laughs.).
ROTFL - Another well-used acronym, it stands for Rolling On The Floor Laughing. Note that you will undoubtedly see ROFL as well, which means the same thing, only the T is dropped from the acronym. You will also see RO(T)FLMAO, standing for Laughing My A** Off.
<g> - This stands for <grin>. Variations on this theme include <eg> for <evil grin>, <beg> for <big evil grin> and, of course, <vbeg> for <very big evil grin>
Then, of course, are the smiley faces. No doubt you've seen them. Some examples:
:) - Your typical smiley face.
=) - Another happy face.
:D - Wide smile.
:( - A frown.
:/ - A confused/disappointed look.
:P - Tongue sticking out.
:Þ - Another tongue. (to do this, hold down ALT, and then on the number pad part of your keyboard, type 0222 and then release ALT)
;) - A winking smiley.
:-) - Just a larger smiley, with a nose.
;-) - Winking smiley, with a nose.
^_^ - Happy
^_~ - Winking
O_O - Wide-eyed with surprise/shock
¬_¬
AKA - Also Known As.
ASAP - You may recognize this one from "real" life... As Soon As Possible.
FAQ - Pronounced as "fack", it stands for Frequently Asked Questions.
GMTA - Not Gates McFadden's Teaching Assistant, believe it or not. It's really Great Minds Think Alike. Variations include SMTA: Simple/Sick Minds Think Alike
IIRC - If I Recall Correctly.
IMHO - In My Humble Opinion. There's also IMO (In My Opinion) and IMNSHO (In My Not-So Humble Opinion).
IRL - In Real Life, meaning the life you lead when you're not logged on to the Internet. (you mean you're supposed to log off?)
j/k - Just Kidding. You may also see this without the slash separating the letters.
NM - Never Mind.
OTOH - On The Other Hand.
TTYL - Talk To You Later.
WTG - Way To Go.
