This caution warns programmers away from relying on the Web SQL Database technology that the W3C decided against standardizing.

An attempt to endow Web-based applications with a means of storing data on the browser's computer is at an end--at least as far as standardizing the technology is concerned.

The technology, called Web SQL Database, built the SQLite database into the browser, letting programmers use the common SQL technology to read and write data. That's useful for a variety of things, but the most notable probably is caching information so it can be retrieved when a computer isn't connected to the network. That's a big problem for many Web apps today.

But yesterday, the World Wide Web Consortium (W3C) deprecated Web SQL, meaning that developers are warned that they can't count on it and that they use it at their own peril. "Beware. This specification is no longer in active maintenance and the Web Applications Working Group does not intend to maintain it further," a prominent note said on the Web SQL Database specification page.

Web SQL had a promising start. Apple and Google were fans, and Opera implemented it, but Microsoft and Mozilla gave it the thumbs down. Instead, those two endorsed an alternative called IndexedDB, also sometimes called IndexDB.

Indexed DB isn't mature enough to use yet by most standards. It's only just arriving in some browsers right now, and the specification is in flux. It is, however, anointed by the W3C.

Web SQL isn't dead altogether. It's still built into several browsers--and not just desktop browsers but the mobile version of Safari in Apple's iOS. So while the technology won't be a standard, expect it to live on at least in some corners of the Web.