Comment by 9dev
3 months ago
While this sounds crazy at first, I could warm for several incremental layers of features, where browsers could choose to implement support for only a set of layers. The lowest layer would be something like HTTP with plain text, the next one HTML, then CSS with basic selectors, then CSS with the full selector set, then ECMA and WASM, then device APIs, and so forth.
Would make it possible to create spec-compliant browsers with a subset of the web platform, fulfilling different use cases without ripping out essentials or hacking them in.
There is no point in several layers because to maximize compatibility developers would need to target the simplest layer. And if they don't, simple browsers won't be able to compete with full-fledged ones.
You can set the doctype in the document to the spec you want to use, which is basically what you're asking for. Try setting <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">