You may enter any font name in the Layout section in the Order Management System. Whether or not it is supported depends on the user's browser. Some fonts, such as Arial and Times, are widely supported. Others, such as cursive, are more questionable. If you choose to use a questionable font, you may enter a secondary choices for browsers that do not support the primary (e.g. "cursive, arial").
Be aware that not all fonts look the same in every browser / computer (IE vs Netscape, Mac vs PC, etc.).