It is not a question of what fonts are supported by W3C or by browsers - it comes down to what fonts people have installed on their computers. If they have it on their computer, it will be used. If they don’t, their browser will use the next one down the stack.
Something to remember is that you don’t have to use web-safe fonts. For example, I like the look and feel of Calibri, but while its market penetration is increasing it is still a long way from ubiquitous. So I include Trebuchet as a back-up, which has a broadly similar kind of shape and form.
Can you upload a font .ttf file to the website folder that the browsers can use as a reference instead of depending on the viewer to have the font installed on their computer?
Yes, that’s usually the stumbling block. You may have purchased a font, but that virtually never comes with a license to redistribute it to everyone else on the Internet. Even the preinstalled fonts on your PC are generally licensed for use on your PC, and not any further afield.
Of course not. Does the browser decide whether you’re downloading a pirated movie or not?
What happens if you do not have a license for a font?
That’s an easy question. The answer is that you’re guilty of theft. You could find your website shut down completely, and find yourself facing a DMCA lawsuit.
Direct from Microsoft: http://www.microsoft.com/typography/RedistributionFAQ.mspx. Don’t be too quickly misled by the “embedded fonts” exceptions. That’s referring to things like a Word document that has some fonts embedded in it. Planting the TTF file on your website, where anyone in the world can get to it, isn’t the same thing.
If you purchased a license that actually allowed you to redistribute the font, you could just stick the font on your website. The owner isn’t going to sue you, if the owner sold you the license.
But a license that includes the right to redistribute the font with no restrictions falls into the “unicorn” category. There is no such thing. If there were, there would be no point in copyrighting the font in the first place.