CSS: Is Helvetica the default 'sans-serif' font on Mac and Arial the default sans-serif font on Windows?

Question

I have a lot of CSS that does the following:

font-family: Helvetica, Arial, sans-serif;

It my understanding that Helvetica is the default sans-

Answer 1

Helvetica on Windows XP looks horrible due to its poor rendering. Luckily, only a few people have Helvetica installed on Windows XP (because if they care about Helvetica, they’ll probably be using a Mac).

This is safer:

"Helvetica Neue", Arial, sans-serif;

That way, pretty much only Mac OS X will pickup Helvetica Neue (standard on OS X) and Windows can ignore it and move straight into Arial.