HTML Basics Section

The role of DOCTYPE? What is the distinction between strict mode and promiscuous mode, and how do I trigger these 2 modes?

<! The doctype> declaration is at the front of the document, before the

DOCTYPE does not exist or is incorrectly formatted to cause the document to be rendered in promiscuous mode.

Strict mode is the browser based on Web standards to parse the page, is a strict DTD, not allowed to use any of the presentation layer of syntax,

Promiscuous mode is a backward-compatible parsing method.

Triggering the standard mode or strict mode is simple, that is, before the HTML declaration of the correct DTD, the starting promiscuous mode can not declare the DTD at the beginning of the HTML document, or add XML declaration before DOCTYPE

HTML Basics Section