DOCTYPE

<..tex4ht doctype ..>

\ifx \a:DOCTYPE\relax
    \:CheckOption{frames}  \if:Option
       <.frames dtd .>
    \else
       <.no frames xhtml DOCTYPE .>
       <.no frames DOCTYPE .>
    \fi
\fi

-_-_-

<..no frames xhtml DOCTYPE ..>

\:CheckOption{xhtml}  \if:Option
    \NewConfigure{@DOCTYPE}[1]{\def\:temp{#1}%
       \ifx \:temp\empty  \let\a:@DOCTYPE=\empty
       \else \ifx \a:@DOCTYPE\relax  \let\a:@DOCTYPE=\empty\fi
         \pend:def\a:@DOCTYPE{#1}\fi}
    \let\a:@DOCTYPE=\relax
\fi

-_-_-

<..configure html4 Preamble ..>

<.pre definitions .>
\Configure{PROLOG}{VERSION,DOCTYPE,*XML-STYLESHEET}
\:CheckOption{mouseover} \if:Option
    <.DOCTYPE in PROLOG under mouseover .>
\fi
\:CheckOption{no-DOCTYPE} \if:Option
   \:CheckOption{no-VERSION} \if:Option
      \Configure{PROLOG}{*XML-STYLESHEET}
   \else
      \Configure{PROLOG}{VERSION,*XML-STYLESHEET}
      <.no-version note .>
   \fi
\else
   \:CheckOption{no-VERSION} \if:Option
      \Configure{PROLOG}{DOCTYPE,*XML-STYLESHEET}
   \else
      <.no-version note .>
   \fi
   \Log:Note{to remove the DOCTYPE declaration
           use the command line option ‘no-DOCTYPE’}
\fi

-_-_-

<..no-version note ..>

\Log:Note{to remove the <?xml version=...?> processing instruction
use the command line option ‘no-VERSION’}

-_-_-

<..no frames DOCTYPE ..>

\:CheckOption{xhtml}  \if:Option
    <.xhtml dtd .>%
    \def\:DTD{xhtml}
\else
    <.html dtd .>%
\fi

-_-_-

<..frames no frames DOCTYPE ..>

\csname a:frames-altDOCTYPE\endcsname

-_-_-

<..configure html4 tex4ht ..>

\NewConfigure{frames-altDOCTYPE}{1}
\Configure{frames-altDOCTYPE}
{<.no frames DOCTYPE .>}

-_-_-

Don’t place the full address ´
’

http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd’ within DOCTYPE. It can stop tools like xt when the server doesn’t respond

<..xhtml dtd ..>

<.xhtml dtd xml-version .>%
\Configure{DOCTYPE}
   {\HCode{<!DOCTYPE html \xhtml:DOCTYPE>            \Hnewline
     
     \Hnewline}}
\def\xhtml:DOCTYPE{PUBLIC
     "-//W3C//DTD XHTML 1.0 Transitional//<.dtd lang .>"\Hnewline
     \space\space
     "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"}

-_-_-

<..dtd lang ..>

\expandafter
\ifx \csname a:dtd-lang\endcsname\relax EN\else
\csname a:dtd-lang\endcsname
\fi

-_-_-

<..xhtml dtd ..>+

\Configure{@DOCTYPE}
{<!ENTITY \% xhtml.dtd \xhtml:DOCTYPE>\Hnewline\%xhtml.dtd; \Hnewline}

-_-_-

<..html dtd ..>

\Configure{DOCTYPE}{\IgnorePar\HCode
    {<!DOCTYPE html PUBLIC
               "-//W3C//DTD HTML 4.01 Transitional//<.dtd lang .>"
     \Hnewline\space\space "http://www.w3.org/TR/html4/loose.dtd">
     \Hnewline}}

-_-_-

<..frames dtd ..>

\:CheckOption{xhtml} \if:Option
    <.xhtml dtd xml-version .>%
    \Configure{DOCTYPE}
    {\HCode{<!DOCTYPE html PUBLIC
           "-//W3C//DTD XHTML 1.0 Frameset//<.dtd lang .>"
     \Hnewline
      "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">\Hnewline}}
\else
    \Configure{DOCTYPE}
    {\HCode{<!DOCTYPE html PUBLIC
                "-//W3C//DTD HTML 4.01 Frameset//<.dtd lang .>"
     \Hnewline "http://www.w3.org/TR/html4/frameset.dtd">\Hnewline}}
\fi

-_-_-

<..tex4ht doctype ..>+

\def\:encoding#1={}

-_-_-

<..xml encoding ..>

encoding="\expandafter\ifx \csname a:charset\endcsname\relax
\expandafter\:encoding\A:charset
\else \expandafter\:encoding\a:charset\fi"

-_-_-

2.3 DOCTYPE