Unicode polytonic Greek
An ancient Greek font must include three accents, two breathings, iota subscript, and the diaeresis (collectively known as diacritical marks), in every relevant combination. For rendering ancient scientific or mathematical documents, it also needs certain archaic letters which were used as numeral symbols. Greek with multiple marks is called polytonic, as opposed to monotonic, which has been formally adopted by the Greek government and uses only a single accent mark.
The simplest polytonic Greek fonts (such as TekniaGreek) assign the diacritical marks by themselves to certain keys, positioned so that they appear over/under the preceding character. This sounds straightforward in theory; but in practice, it is difficult to get the marks to align properly, since the vowels differ in width. Additionally, web browsers may not be consistent with mark placement depending on the size of the browser window and the position of the line breaks.
A more complicated way of rendering the font is to include every necessary letter/diacritic combination as a preformed character in the font file. This method is more “foolproof” as to appearance, but the large number of characters necessitates special provisions for typing the characters. In the past, there was no standard for where to assign the characters in a font, and the users of different fonts could not read each others’ documents.
Unicode® is an international standard for assigning key codes to the characters of potentially every alphabet and language system in the world, making all Unicode-based systems mutually intelligible. It uses a vast number of character codes outside the standard 127-character set that non-Unicode fonts use, and all modern browsers and operating systems support it.
Note that since the Unicode characters for different alphabets are outside the standard ASCII (keyboard) range, dedicated utilities are required to type them; see the technical information page for more information.
On the next page are links to internet sources for a number of Unicode polytonic Greek fonts, with samples and more information. I have created the Aristarcoj font which includes all of the Greek chararacters, including numerals, and Coptic characters. It is in the process of being updated.
Unicode polytonic Greek fonts
Technical information about Unicode Greek on the web