Loser's Guide to Life
Something that science fiction movies of the recent past sometimes missed was the development of personal computers. I was watching a movie made not too long ago in which the characters, surrounded by magical 30th century technology, run to their computer to find something out. POCK POCK POCK POCK POCK. POCK!, the hero “enters” a query on the crummy old keyboard and everyone strains to see what turns up on the blinking little dark screen. What they failed to predict wasn't so much any improvement but the fact that computers would be more handily adapted for casual use, or that computers would gradually become like any other human tool, like an adze or a thimble.
In the Zone the other day I saw that every second person was looking at a tiny notebook as they drank their coffee. You see?? It's a codex, the great invention of the second century. Before then, people had to read things on scrolls, which have to be scrolled through. If you've had occasion to search lots of rolls of microfilm you'll appreciate the nuisance level.
And so they invented the codex and, thereby, the page suitable for the individual reader. People had had leaves before, but they could be any size, and generally only one side had writing on it. In a codex, the leaves all have to fit in the covers, and both sides (or pages) are used. And of course the thing itself is meant to be carried around comfortably, in a pocket or satchel. And the size of the page? Eight and a half by eleven seemed good, because, to the normal reader holding a text, this is what you can see clearly without moving your head. You can see way more, but not attentively, with both eyes.
(Hence the Russian expression smotret' v oba, “use both eyes!” To get a good, stereoscopic look at something, both eyes have to be the same distance from the thing.)
And that's why many webpages are designed to be around 700px in width. That's roughly seven and a quarter inches, which is like an eight-and-a-half-inch page with some breathing space at the edges, five eighths of an inch.