Because we cannot see each other's facial expressions, or hear the tone of voice, when we are communicating by email or on a message board or in a chat room, it is difficult to tell what the real meaning is - was that supposed to be sarcastic? supportive? was he laughing at me?  So we use emoticons to show our expressions.  Here are some of them:

 

 

or :-) Expresses happiness, sarcasm, or joke
or :-( Expresses unhappiness
:] or :-] Expresses jovial happiness
:[ or :-[ Expresses despondent unhappiness
or :-D Expresses jovial happiness
:I or :-I Expresses indifference
:-/ or :-\ Indicates undecided, confused, or sceptical. Also .
:Q or :-Q Expresses confusion
:S or :-S Expresses incoherence or loss of words
:@ or :-@ Expresses shock or screaming
or :-O Indicates surprise, yelling or realisation of an error ("uh oh!")


Acronyms - net shorthand

AAMOF as a matter of fact
BBFN bye bye for now
BFN bye for now
BTW by the way
BYKT but you knew that
CMIIW correct me if I'm wrong
EOL end of lecture
FAQ frequently asked question(s)
FITB fill in the blank
FWIW for what it's worth
FYI for your information
HTH hope this helps
IAC in any case
IAE in any event
ICL in Christian love
IMCO in my considered opinion
IMHO in my humble opinion
IMNSHO in my not so humble opinion
IMO in my opinion
IOW in other words
LOL lots of luck or laughing out loud
MGB may God bless
MHOTY my hat's off to you
NRN no reply necessary
OIC oh, I see
OTOH on the other hand
ROF rolling on the floor
ROFL rolling on the floor laughing
ROTFL rolling on the floor laughing
RSN real soon now
SITD still in the dark
TIA thanks in advance
TIC tongue in cheek
TTYL talk to you later
TYVM thank you very much
WYSIWYG what you see is what you get
<G> Grinning
<J> Joking
<L> Laughing
<S> Smiling
<Y> Yawning