1337 (written in ASCII) - From the word Leet, derived from the word elite
2 - too, or to , Two
4 - For , Four

A

AFAICR/S/T - As far as I can recall / remember / see / tel
AFAIK - As far as I know
AFK - Away from keyboard
ANFSCD - And Now For Something Completely Different. Used to change the subject of conversation.
ASAP - As soon as possible
ASL - Age / sex / location
ATEOTD - At The End of the Day
ATM - At the moment
AWOL - Absent Without (Official) Leave
AYBABTU (also abbreviated as AYB) - All your base are belong to us (from the video game Zero Wing)

B

B2B - Business to Business
B& and/or B7- Banned
BBIAB - Be back in a bit
BBL/S - Be back later / shortly / soon
BCNU - Be seein' you
Blog - Also known as web log or an online journal
BOFH - ~censored~ operator from hell
Bot - Any type of automated software in chatrooms and web-cataloging software
BRB - Be right back
BSOD - Blue Screen of Death
BTDT - Been there done that
BTW - By the way
Bump - Increment (For example, C's ++ operator.)or a backronym for "Bring Up My Post"

C

Crawl - To retrieve a web page along with the hyperlinks that reference it
Crapplet - A poorly written computer application
CU - See you (later)
CYA - See ya OR Cover Your Ass
Cyber (prefix) - A term used to connect the subsequent word loosely to the world of computers or the Internet or sex over a computer
Cyberspace - Virtual reality, the Internet, the World Wide Web, and other kinds of computer systems. Science fiction author William Gibson popularized the term in his novel Neuromancer. Gibson used the word to describe a virtual world of computer networks that his cyberpunk heroes 'jacked into'

D

DFTT - Don't feed the trolls
DGAF - Don't Give A ~censored~
DIAF - Die in a fire
DILLIGAF/D/S - Does it look like I give a flip / ~censored~ / damn / ~love~
DND - Do not disturb
DOA - Dead on arrival. Refers to hardware that is broken on delivery.

E

EOF - End Of File
EOM - End of Message
EOL - End of Life. Device or hardware that is at the end of its product life cycle.
EQ - EverQuest
ETA - Estimated time of arrival

F

FAQ - Frequently Asked Question(s)
FFS - For ~censored~'s sake
Flamer - Someone who makes inflammatory, abusive or directly offensive comments. Similar to, but not quite the same as an Internet troll[3]
FMCDH - From My Cold Dead Hands
FOAD - ~censored~ off and die
FOAF - Friend of a friend
FTL - For the loss
FTW - For the win
FU - ~censored~ you
FUBAR - ~censored~ up beyond all recognition / repair (from military slang; pronounced "foo-bar")
FUD - Fear, Uncertainty and Doubt (the purposeful spread of misinformation)
FWIW - For what it's worth
FYI - For your information

G

GBTW - Get back to work
GF - Great/good fight/girlfriend
GFU - Good for you
GFY - Go ~censored~ yourself
GG - Good game, used at or near the conclusion of a gaming match
GJ - Good job, often used in online gaming when a teammate performs an act benefitting his team, such as killing an opponent or enabling that kill
GMTA - Great minds think alike
Godwin's Law - Dictates that the longer a thread, the more likely someone will post a comparison involving Nazis or Hitler
Gratz - Congratulations
GTFO - Get the ~censored~ out
GTG or G2G - 'Got to go' or 'Good to go'
GR -Good Race
GR8 - Great

H

HAND - Have A Nice Day
Handle - Name used in online chat, (AKA nick(name), alias, screen/user name)
HF - Have fun
Haxor or H4x0r (1337) - Hacker
Hit - A request made to the web server, (noun) the results of an internet search, (verb) loading a Web page. Hits are not equivalent to visitors of a webpage.
Home page - The website's introduction page, starting point, and guide. The technical term is "index"
Hot list - A collection of publicly available URLs (World Wide Web site addresses), sometimes available as text files.
HTH - Hope this / that helps
H8 - Hate