What Fonts Are Included (I.E. Installed by Default) with Which Operating Systems

What fonts are included (i.e. installed by default) with which operating systems?

OS X - http://en.wikipedia.org/wiki/List_of_typefaces_included_with_Mac_OS_X

Windows - http://en.wikipedia.org/wiki/List_of_Microsoft_Windows_fonts (Includes all windows version, but it notes next to each font which one is for which version(s)

Also, see this for a list of fonts common to both http://www.ampsoft.net/webdesign-l/WindowsMacFonts.html

Glyph coverage for Unicode characters in various OS

I don’t thin there is any site of the caniuse.com type for characters; it would be a rather large site, and maintaining it would be a nightmare. I quickly souped up a short section “Which characters can I use” that I added to my Guide to using special characters in HTML, but it’s really just a few hints.

The good news is that nowadays the issue is mostly font support to characters, and this can often be handled by setting up a suitable font-family list in CSS. Browsers cannot always pick up a character from a font unless the web page author gives a helping hand that way.

Using only serif as font in CSS

On Windows, it's Times New Roman. On Mac, it's Times, though it may be Times New Roman as well.

What are good web development fonts?

See this list of browser safe fonts.

It's Windows+Mac centric, but still applies. They do include a linux distribution screenshot, as well.

font-family: Garamond, sans-serif; won't always produce sans serif font face, why?

As Alochi said, Garamond is a serif typeface. Your second pic is what Garamond is supposed to look like. The computer for your first pic did not have Garamond installed, so it used "sans-serif" (in this case, Arial) instead.

Garamond is not distributed with any Windows version. It is included with Microsoft Office, which is why many Windows PCs have it.

Any computer, with any OS, that has Garamond will give you a serif font, so if you don't want serifs, you must not call for Garamond.

Is Helvetica a browser base font?

No, Helvetica is not a "base font".

The best definition of "bast font" is probably Microsoft's Core Fonts for the web, and Helvetica's not there.

If you want Helvetica, you either have to get a Mac (it's one of the default fonts on mac OS X), or buy it from Linotype (the company that owns it).

What Fonts Are Included (I.E. Installed by Default) with Which Operating Systems