Glossary Web Standards
Web Standards
TechWeb Standards
Definition
The open specifications — HTML, CSS, DOM, HTTP, ECMAScript, WAI-ARIA and the rest — that browsers implement in common, maintained by the W3C, WHATWG, IETF and TC39, so that a page written to them works in any conforming browser without being written for one
The reason semantic HTML is most of accessibility, the reason progressive enhancement is possible at all, and the reason a page from 2005 still renders. The site's own rulings put semantics before visuals for this reason: the standard is the durable part.
The contract between everyone who writes for the web and everyone who renders it. Build to the standard and the browsers come to you; build to a browser and you go back every year.