Another staple of online communication, ha ha is sometimes substituted for the overused lol. Ha ha however, may intonate subtle sarcasm depending on context.
Mary: "My computer won't play any sound."
John: "Ever heard of a volume knob?"
Mary: "I know how to work a knob."
John: "I bet you do."
Mary: "ha ha"
If capitalized, it is generally in response to something genuinely funny. HA HA.
Not to be confused with heh heh, which denotes a slightly devious or subversive undertone. Similarly, if ha ha is preceded by muah, as in muah ha ha ha it can reflect an overt deviousness.
An extremely twisted sense of humor can be conveyed by capitalization (MUAH HA HA HA, or MUAHAHAHAHA).
An intentionally goofy, or sarcastically stupid laugh would be expressed as hur hur hur, or huahuahua.
tee hee is sometimes used as a flirty come-on response to a lewd comment.
Also be aware of the Spanish spellings, ja ja ja, and jai jai jai.