Unfortunately SHORTTAG and SHORTREF were enabled in the SGML
declaration for HTML 4.  There are two different places where I would
modify the SGML declaration for HTML4 in order to have the document
type function in a way that is consistent with the historical behavior
of most browsers.  Diffs follow:
---------------------------------------------
<                   SHORTREF SGMLREF
---
>                   NESTC "/"
>                   NET ">"
>                   SHORTREF NONE
---------------------------------------------
<     SHORTTAG YES
---
>        SHORTTAG
>            STARTTAG
>                EMPTY NO
>                UNCLOSED NO 
>                NETENABL IMMEDNET
>            ENDTAG
>                EMPTY NO 
>                UNCLOSED NO
>            ATTRIB
>                DEFAULT YES
>                OMITNAME YES
>                VALUE YES
>        EMPTYNRM YES
>        IMPLYDEF
>            ATTLIST NO
>            DOCTYPE NO
>            ELEMENT NO
>            ENTITY NO
>            NOTATION NO
---------------------------------------------