Back in the 1990s, when Tim Berners-Lee and his team were creating the infrastructure of the World Wide Web, they made a list of the error codes that would pop up when something went wrong. You've surely encountered many of them: "404 Not Found," which pops up if you click on a dead link; "401 Unauthorized" when you hit a page that needs a password; and so on.

Here's one you probably haven't seen—and its absence from your life speaks to why the promise of the early web seems increasingly out of reach: "402 Payment Required."

That's right: The web's founders fully expected some form of digital payment to be integral to its functioning, just as integral as links, web pages, and passwords. After all, without a way to quickly and smoothly exchange money, how would a new economy be able to flourish online? Of course there ought to be a way to integrate digital cash into browsing and other activities. Of course.

Yet after almost three decades, that 402 error code is still "reserved for future use." So I still have to ask: Where are my digital micropayments? Where are those frictionless, integrated ways of exchanging money online—cryptographically protected to allow commerce but not surveillance?

I don't really want a flying car, but I do want to be able to shed pennies (and fractions of pennies) as I browse news or read fiction online. I want to easily support artists and writers without having to set up an account, create a password, fork over my credit card details, and commit to an ­ongoing­ relationship that involves receiving a new piece of spammish email at least once a week.