As you probably know, the default value is a value that the browser assumes if you have not told it otherwise. A good example is the font size. The default font size is 3. If you say nothing it will be 3. If you make faces at your computer it will still be 3.
Every browser has a default font setting- font name, size and color.
Now with Netscape 3.0 we can specify font names other than the defaults. Something really cool The font will only display if your viewer has that font installed on their computer. If the person looking at the page doesn't have installed on their computer the font you specify, then they will only see the default font. So be very judicious in your use of fonts. Arial and Comic Sans MS are pretty widely distributed with Windows.