Not all fonts have all the special symbols. Arial and Times new Roman DO have them. So the above means that you need to choose fonts which are more than likely to be in the users' system. In the illustrative tables which follow I am showing you the fonts as text on the left and as graphics on the right. The text fonts may not appear correctly if your system does not have the appropriate font installed.
Every computer has a default serif, sans-serif and monspaced font.
These fonts are available in the systems of all computers of the particular make concerned. Unfortunately you will see that although you can be certain that a PC has its three fonts specified above you cannot be sure they will be available on a Mac and vice versa. There isn't even the obvious equivalence mapping between these fonts built into web browsers. This means that a page which uses Arial displayed on a Mac without Arial will be displayed in Times, the browser's default font, not Helvetica. You can extend the format of the FONT tag to supply a set of font names.