When a doctype is present, browsers will render the page in mode, employing the most current specifications of hypertext markup language (html).
quirks
standards
supervisor
protected

Standards Mode

Explanation:

The old implementations for web pages where typically for Netscape Navigator and Internet Explorer browsers. However when standizations were made by W3C, implementing these new standards by mordern browsers on the old websites was going to lead to problems as these browsers will be unable to render websites that were build from the past.

Therefore, web browsers introduced "Modes",  in this way, mordern sites (Those in compliant with W3C, standards) and Old sites built in the past can be treated differently by the web browsers. These modes are Quirks, Almost Standard and Full Standards. The Standards Mode ensures that the web page is rendered according to the specified HTML and CSS in the source code. Web browsers will use a DOCTYPE in the beginning of a HTML file to decide on rendering the page in a standards mode.

(because i need 20 chars)