I have seen a few of the the websites using font family:
font-family: 'Helvetica Neue',Helvetica,Arial,Sans-Serif
I remember reading in some older question here on Stack Overflow that the Helvetica font is not free, and it is available on Mac only, is it so? I'm using Windows XP and I can see that font being rendered is 'Helvetica Neue', and I don't remember installing any font by myself. so all I wanted to ask is if it is safe to use the above font family? (e.g. will most of the Windows computers render those fonts?)
Helvetica comes free with Mac but not with Windows. You will have to buy it. But if you have installed Adobe products, it will be installed with many other fonts that come packed with Adobe.
'Helvetica Neue' is the newer version and has slight modification than the older one with correction of few problems that occurred with Helvetica.