The way to expressing emotions in Japanese sites

Sometimes we can find some distinctive marks or signs to express emotions in Japanese sites.

for example
sign    meaning
(笑)    laughing
(怒)    angering
(汗)    impatient
www   laughing

It are used almost personal blogs not official sites.
The company's or organization's site don't use that letters

笑,怒,汗, are all kanji character, 笑 means laughing, 怒 means angering, 汗 means sweat originally but turning to meaning to impatient.

Why does "w" mean laughing, laugh say "warau" or "warai" in Japanese so they have used the first letter "w" to express laughing.
In occagion big laghing are to be written as
"wwwwwwwwwwwwwwwwwww"

Are you hearing their laghing voice seeing "www"?
Wahahahahaha.