SGML DTD for Internet Explorer 3.0 Markup

Mark Buckley
Microsoft Corporation

November 12, 1996

Formally, HTML is an application of Standard Generalized Markup Language (SGML) -- that is, HTML follows the rules of the international SGML standard (ISO 8879). An SGML language is specified in large part by a Document Type Definition (DTD) that defines the tags an author may use to mark up a document.

The World Wide Web Consortium (W3C) has published and continues to evolve SGML DTDs for HTML. However, due to differences between the processes of standards development and applications development, at any given time Internet Explorer may support extensions to, or minor modifications of, the basic markup defined by W3C. The download provided above includes three files that constitute an SGML DTD describing valid HTML markup for Microsoft Internet Explorer 3.0:

The principal file, IE30.DTD, defines markup for HTML headers and document bodies.
The IETABLES.DTD file contains table markup.
The IE30-S.DTD file invokes "strict" HTML markup.

The DTD for Internet Explorer 3.0 has been derived directly from the W3C draft DTD for HTML 3.2 known as the "Wilbur" DTD

, dated May 1996. All Internet Explorer 3.0 extensions as well as many Netscape Navigator extensions have been added. The DTD for tables has been derived directly from the table markup portion of IETF's now expired draft DTD for HTML 3

, dated March 1995.

The DTD defines, first of all, HTML that works with Internet Explorer. That is, if your HTML document parses according to this DTD, it should be handled correctly by Internet Explorer 3.0.

Moreover, the DTD describes the "intentions" of Internet Explorer. Because Internet Explorer is designed to be very "accepting", it's quite possible to write HTML that does not conform to this DTD but that will display acceptably in Internet Explorer anyway. We recommend, however, that HTML documents created for use with Internet Explorer do follow the grammar defined in the DTD to allow for more predictable results as both HTML and Internet Explorer continue to evolve.

Caveats

The DTD contains some Netscape extensions that Internet Explorer does not support, as well as some table markup attributes that appear in the IETF HTML 3 Tables DTD, but that Internet Explorer does not support. Because we do not want HTML containing such markup to be rejected by a validating parser, we have included them in the DTD. These attributes are commented on in the DTD.

This is a beta DTD. We expect some bugs. We also expect some disagreements about coding strategies for some of the more problematic aspects of the markup; for example, how to code the <CENTER> element. We encourage comments; send e-mail to Chris Wilson (cwilso@microsoft.com) and/or Mark Buckley (mbuckley@microsoft.com).