HTML: Doctype

What is Doctype

DOCTYPE is a document type declaration, for HTML and XML.

• It must be on the first line of a file.
• It is required.

• case-insensitive for HTML.
• case-sensitive for in XML (XHTML).

HTML 5 (year 2014)

practically, use this for any html created after year 2014.

<!doctype html>

or

<!DOCTYPE html>

Old Doctypes

HTML 4.01 transitional

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

HTML 4.01 Strict

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

HTML 4.01 Frameset

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">

XHTML 1.0 transitional (Corresponding to HTML 4.01 transitional)

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">