CSS font-family displays differently on Windows and Mac OS X

Question

For some reason, the following two code snippets display correctly on Mac OS X but are completely ignored on a Windows i.e. the font reverts to Times New Roman with default sizes and margins. Any idea why this could be?

body {
    font-family: "Helvetica Neue", "Lucida Grande", "Sans serif";
}

#div h1, p {
    margin: 0px;
    font-size: 14px;
    color: #333;
}

Answer 1

It's sans-serif with a dash. The first two fonts are probably not installed on the Windows PC (I don't have them).