Pink- No question is a dumb question!
Feel free to ask away here.

LMAO= laughing my ass off
LMFAO= laughing my fucking ass off
Rotflmao=Rolling on the floor laughing my ass off
Rotflmfao= you probably get the idea from the two above
NP= No problem
OMG= Oh my God
TTYL=Talk to you later

That's all I can think that we use commonly around here.. but feel free to post any I might of missed and someone will be happy to reply.