Doctype is required in HTML document for legacy reasons. Its main purpose is to prevent the browser from entering 'Quirks Mode' while rendering the document.
Including the DOCTYPE in a document ensures that the browser makes the best-effort to follow standard specifications. The doctype should be included at the beginning of the HTML document as shown in the example, below.
<!DOCTYPE html> <html> <head> <title>Including Doctype in HTML Document</title> </head> <body> <h1> Including Doctype in HTML Document </h1> <p> Welcome to hackinbits.com </p> </body> </html>
In HTML5, Doctype's only purpose is to activate the full standard mode.