Hi,
I have read that the exclamation point is used to indicate stronger that usual feeling, such as surprise, anger, joy, or raised voice level, etc.
Of course we also use it for negation in computer language such as: "if A!=B then goto Start else goto Ender"
So it makes sense to me, although i think 2 in a row is supposed to be the limit. It doesnt bother me though if i see more because this seems to be accepted practice on the internet.
Also, there is supposed to be no space after the last letter just before the mark, but i use a space on many web texts because it's easier to see with these computerized fonts whereas in written language it's easy to see without the space. So i regularly violate the "no space" rule so people can see the mark better.
Example:
I could not believe it was raining outside today again !
instead of:
I could not believe it was raining outside today again!
Depending on the font the first one is easier to read.
Compare these two:
That song was very joyful!
That song was very joyful !
The first one on my screen looks almost like "joyfull".