Un documento valido di HTML/XHTML dichiara nel documento che versione di HTML/XHTML � usata. Il tipo dichiarazione del documento chiama il DTD (Document type definition) in uso per il documento.
HTML 4.01
HTML 4.01 specifies three DTDs
Strict DTD
Transitional DTD
Frameset DTD
Gli autori devono includere uno del tipo dichiarazioni del documento nei loro documenti. Il DTDs varia negli elementi che sostengono.
Strict DTD
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
Transitional DTD
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01
Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
Frameset DTD
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN"
"http://www.w3.org/TR/html4/frameset.dtd">
XHTML 1.0
XHTML 1.0 specifies three DTDs
Strict DTD
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
Transitional DTD
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
Frameset DTD
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">
XHTML 1.1
DTD
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
Keywords:xml document, xml schema, w3c xml schema, xml parser
