The HTML 4.01 specification provides several different types of doctypes that allow different types of elements to be specified within the document.

HTML 4.01 Strict

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

Includes all HTML elements and attributes, but does not include presentational or deprecated elements and framesets are not allowed.

HTML 4.01 Transitional

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

Includes all HTML elements and attributes and presentational and deprecated elements, but framesets are not allowed.

HTML 4.01 Frameset

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

Includes all HTML elements and attributes, presentational and deprecated elements. Framesets are allowed.