Here are some of the most common:

:( Writer is sad

:-) Writer is happy or smiling (yer basic smiley)

:-# Writer has lips sealed

;-) Wink

>:-< Writer is angry

:-J Tongue in cheek

() Hugs

:-O Writer is surprised

:* Kiss

:** Returning kiss

:-P Sticking tongue out

:-& Writer is tongue tied

%+( Beaten up

R-) May glasses are broken

:-e disappointed

:-)' Drooling

>:-) evil grin

:-! Foot in mouth

:*) has a cold

:-C jaw hits the floor

.-) keeping an eye out

:-D laughing out loud

:^) nose out of joint

:-V shouting

:-W speaks with forked tongue

:-T tight lipped

:-/ undecided

There's loads more, why not see if you can figure them out of even invent your own!!

An acronym is a very short set of letters that represent a word or phrase. These are used quite a lot on the internet.

Here's some of the most common:

AFAICT as far as I can tell

AFAIK as far as I know

AFK away from keyboard, BAK back at keyboard

AIUI as I understand it

B4 before

BCNU be seeing you

BBL be back later

BSF but seriously folks

BTDT been there done that

BTSOOM beats the shit out of me

BTW by the way

CUL see you later

DWISNWID do what I say, not what I do

F2F face to face

FOC free of charge

FWIW for what it’s worth

GA go ahead

FYA for your amusement

FYE for your entertainment

FYI for your information

<G> grin

GIGO garbage in garbage out

HHOJ ha ha, only joking

IAE in any event

IIRC if I recall correctly

IME in my experience

IMHO in my humble opinion or just IMO

IMNSHO in my not so humble opinion

IOW in other words

IRL in real life

ISTM it seems to me

ISTR I seem to recall

IWBNI it would be nice if….

IYSWIM if you see what I mean

JAM just a minute

KISS keep it simple, stupid

L8R later

LOL laughs out loud

MORF male of female?

NALOPKT not a lot of people know that

NRN no reply necessary

OAO over and out

OBTW oh, by the way

OIC oh I see

OTOH on the other hand

PITA pain in the arse

RSN real soon now

RUOK are you okay?

SITD still in the dark

TANSTAAFL there ain't no such thing as a free lunch

TCB trouble came back

TDM too damn many

TIA thanks in advance

TIC tongue in cheek

TNX thanks

TVM thanks very much

TPTB the powers that be

TTFN ta ta for now

TTYL talk to you later

UBD user brain damage

WRT with regard to

See if you can think up any more, it's fun!