I was explaining to someone my scale of online laughing. I have explained it before, but here it is, in summary:
Haha=I acknowledge that you are saying something meant to be humorous. I may or may not find it funny, but I'm letting you know, that I know, that you think it's funny.
Hahah=I actually find what you said to be amusing. I definitely laughed, but it may or may not have been out loud.
Hahahahhah (or some form of multiple hahas)=This means that you have made me laugh, out loud. I am possibly cracking up. Ending in an 'h' indicates a heartier laugh, as I was clearly laughing so hard, that I have completely disregarded the correct spelling of the word 'haha'.
Hah=This one is complicated because it has so many meanings. The first is, what you said was not intended to be humorous and I don't know what else to say, therefore the 'hah' becomes a filler. The second, you have said something meant to be funny, but I don't find it funny--at all. It can also be used when I am laughing at some sort of pun that is worth a chuckle at its clever, yet dumb nature.
Ha=You are trying to be funny, and I just don't care to humor you, yet cannot disregard your attempt.
Other Internet Laughing
There are other forms of laughing I OCCASIONALLY use on the internet, however, I rarely veer from the "Haha System":
LOL: Used quite rarely by me, partially as a reaction to the LOL epidemic sweeping my generation.
Example--"john that is like soooo funny lol. i can't believe u ate that lol. lol ur crazy lol."
Another reason not to use "LOL"? If someone says something, and you respond "Laugh out loud", what you generally mean is, "Laughing out loud". As in, I am laughing out loud right now at your hilarious comment. Therefore LOL is gramatically incorrect, and I just can't have that. Sometimes, I will resort to LingOL to fix this problem, or I will simply tell someone that I am "actually laughing out loud". Yes, I realize that this is defeating the purpose of the shorthand, but it makes me feel better and I will continue to say it as I see fit.
Lastly, and probably most importantly, if you say to someone "LOL" and you have not, in fact, laughed out loud, you are a liar. Period. Try and live with that.
Jaja: Spanish version of "haha". Used when I am feeling exotic.
COTI: Chuckling On The Inside. A much more acceptable version of the "LOL" because it is telling the truth. No need to hide your true reaction through false acronyms. Just tell the world that their jokes were funny enough to cause a chuckle on the inside, but certainly not enough to warrant laughing aloud.
And, that, is the complexity of laughing. No joke.