If I type 'lol' I have said 'ha!' and smiled. This could mean that I am acknowleging irony, sarcasm, etc. I may also be laughing at myself, which is something I try to do as often as possible.
If I type 'LOL', I have said 'ha ha' and smiled longer. This could mean that I thought what I read was pretty cute or reasonably funny. This also could mean that I am really amazed by my own stupidity.
If I type LMAO, ROTF, or ROTFLMAO, that means I had a laughgasm, and I thank you.
There, now you have the key!
