Toward a standard font size interval system

Todd Fahrner, Verso
This document is under construction, so you’ll encounter a few “staircases into air,” non-sequiturs, etc. Bear with me. If you’re really keen on this stuff, and can’t wait for me to get it together here, you might do an advanced search at Deja for “fahrner pixel” and review the threads turned up from the “mozilla” newsgroups.

Note: This document contains exhibits that are styled extensively with Cascading Style Sheets (CSS1). These exhibits are known not to display with a useful degree of accuracy in any released version of Netscape Navigator/Communicator. I have certified adequate accuracy only in recent versions of MS Internet Explorer. If in doubt, please visit with Explorer.

Abstract
The problem
Generalities
Specifics
The solution
Trouble in paradise: the CSS keywords
Building a better scale
Increments and decrements
Synoptic table
A mathematical excursus
Implementation implications
User interface assumptions
Abstract
This document discusses the strengths and weaknesses of various deployed and recommended methods of specifying font sizes in Web documents and application interfaces, and proposes a harmonization. This scheme will enhance the legibility, clarity, and aesthetics of documents presented on screen, and help retire less elegant alternatives that are hurtful to the Web as a dynamic information resource – one that is accessible to users with widely varying needs and purposes. It is intended for Web browser and stylesheet implementors of all religions, but may be of interest to Web authors and digital typography and/or CSS enthusiasts at large.

If you think the subject matter is important, and disagree or don’t understand, please either contact me or bring it up in an open forum such as the W3C’s www-style mailing list.

The problem
Generalities

/> Font size modulation is a fundamental typographic design technique. Size does matter. A reader can discern the structure of documents at a glance when their internal structure is reflected (among other things) by relative font size changes. Larger type is for headings or emphasis, smaller type is for deemphasis, and medium type is, well, medium. In high-resolution print typography, designers enjoy considerable freedom and control over the articulation of this range. In low-resolution screen typography, designers don’t.

There are many problems associated with displaying font size ranges distinctly and attractively at low screen resolutions. Part of the difficulty stems from the variable design and quality of fonts themselves, for which a partial solution has already been recommended. This piece addresses a more elementary problem: the need for (and lack of) a standard font size interval system.

“Two steps smaller” or “extra large” have no normative default meanings across applications or platforms (i. e., on the World Wide Web). This means that when designers avail themselves of such expressions, the results are often unexpectedly crude or illegible. Desperate or naive designers usually seek relief in inflexible pixel or print-specific absolute units such as points instead. The worst case is common practice: the designer simply turns most or all text into graphics.

While the problems are subtle in nature, they are profound in effect: people often can’t read on screen, or can read only with discomfort. Ironically, as the powerful, ill-implemented, ill-understood Web typography language CSS begins to see wider use, the problems grow more acute.