See the original/official version of the proposed text: http://www.ornl.gov/sgml/wg8/document/1935.pdf, from which the following unofficial excerpt is taken.
The Hypertext Markup Language is an SGML application conforming to International Standard ISO 8879 -- Standard Generalized Markup Language (SGML). It provides a simple way of structuring hypertext documents which refer to one another and which collectively create an enormous "web" which continues to grow and evolve as many hypertext authors add and modify documents.
The web has expanded and browser developers have added additional features to the markup language such as new tags and new semantics for the tags. As a result, many documents have been created which can only be rendered faithfully on a limited number of browsers. Common web practice is to hide any syntactic problems detected by the browsers and thus the reader is not always aware that the page being browsed is not faithful to the original authored document.
This Final CD has been developed in an effort to ensure that it will remain possible for an author to produce simple hypertext for the web and be confident that a conforming browser will be able to render the document faithfully. This specification represents a core of the language to be supported by all conforming browsers, authoring and validating systems, and provides techniques for extending the core that are SGML conformant and represent good SGML practice.
The language defined by this Final CD is a refinement of the W3C Working Draft 17-Sep-1997 for HTML 4.0 and provides additional specifications for the use of that document. All conforming ISO-HTML documents also conform to the W3C Working Draft 17-Sep-1997 for HTML 4.0. ISO-HTML omits all deprecated features of the language, features whose role is purely cosmetic, and features which are still unstable or immature. This has been done in preparation for the expected future introduction of style sheets. Certain optional facilities such as markup omission of the document element and the major elements have been removed to produce more robust texts in keeping with recognized good SGML practice. This does not reduce in any way the expressive power of the language.
It is recognised that some HTML documents are generated from other structured sources and further processing is not intended. Authors wishing to simplify the production of ISO-HTML in such a case may omit the Structure facility which eliminates the need to respect the correct structuring of sections.
Although this Final CD recommends the complete separation of content and style, it is simpler for authors creating documents that are not intended for re-use to include style information with the document. To support this practice the InLineStyle facility allows style information to be placed in the document. The style language is not defined by this specification.
Many popular user agents do not support the full power of SGML and are unable to parse the document type declaration subset. To facilitate the use of such browsers, the DTD has been packaged to allow reference to the DTD including facilities such as InLineStyle and Structure without having any internal subset.
The conformance statements in this specification distinguish between a conforming system and a validating system. Conforming systems behave correctly when processing conforming documents, but are not required to handle broken documents. Validating systems are required to identify all SGML and ISO-HTML errors, and must be able to certify that a document is valid ISO-HTML. Commercial browsers are usually conforming systems, whereas authoring systems are usually validating systems.