Which do you prefer, when writing on a greeting card or FB wall?
I do neither of those things, but I loathe excessive capitalization.
The first one
“Happy Birthday” is a song. I use the latter.
For Facebook I use, “Happy, happy, happy, happy!” or some variant. They know it’s their birthday.
I’ll write “Happy Birthday.” I can’t believe anybody is actually bothered by it or would be ill-mannered enough to criticize me for it.
I’ll write “hap bday” because I don’t have time for extra characters with my go-go lifestyle.