Strict mode and promiscuous mode

Strict mode is the browser based on the Web Standard to parse the page, is a strict DTD, not allowed to use any of the presentation layer of syntax, such as <br/>.
What is promiscuous mode?

Promiscuous mode is a backward-compatible parsing method, and the transparent point is that it can implement the rendering mode of the browser IE5.5 the following versions.
Trigger Strict mode

Trigger Strict mode is simple, is the normal establishment of the Web page, declaring the correct DTD, is the strict mode.
Trigger Promiscuous Mode

The trigger for promiscuous mode can be implemented by not declaring the DTD at the beginning of the HTML document, or by adding the XML declaration l<?xml version= "1.0〃encoding=" utf-8〃?> before doctype.

Strict mode and promiscuous mode