On codices and conventions

As I was reading Robert Darnton's The Case for Books, one word in particular jumped out at me, one which I hardly remembering hearing since high school: codex. Random house defines it by way of another delightfully arcane term:

a quire of manuscript pages held together by stitching

A quire, in turn is a set of folded leaves of paper or parchment (particularly, a set of 24 or 25). In other words, the distinctive feature of the codex is that it has pages, as opposed to a scroll or tablet. Here's a broad view from Darnton of what this meant:

The history of books led to a second technological shift when the codex replaced the scroll sometime soon after the beginning of the Christian era. By the third century AD, the codex — that is, books with pages that you turn as opposed to scrolls that you roll — became crucial to the spread of Christianity. It transformed the experience of reading: the page emerged as a unit of perception, and readers were able to leaf through a clearly articulated text, one that eventually included differentiated words (that is, words separated by spaces), paragraphs and chapters, along with tables of contents, indexes, and other reader's aids.

I would parse this as one major technical shift — from a single, serial scroll to random-access pages — and several refinements in convention — inter-word spacing, paragraphs, chapters, tables of contents, indexes, etc. This seems very much analogous to the case of conventions on the web. In both cases the technical shifts (script-enabled browsers in the web case) are important, but they are relatively rare. Small shifts in convention (tabs, rollover highlighting, etc.) are more common, and just as important in the aggregate.