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
Are you hearing their laghing voice seeing "www"?