HTML is evolving, new tags are being added at a steady pace. Once the browser developers are done implementing the eminently useful blink tags, drop-caps, and what have you, we may perhaps see the emergence of a table model, style sheets, and other tidbits that would be slightly more useful. Especially the notion of standardized style sheets would be a boon in addressing some of the more adventurous excursions in HTML-land. HTML markup, as it is being used today, is flat . There is no concept of encapsulation and HTML tags are being applied in a linear manner.
Complex documents are hierarchical documents.
Until HTML truly supports hierarchy and the browsers let you explore and use this hierarchy, HTML remains unsuitable for technical or lengthy documents, whereas SGML, as we all know, is a prime choice for this task. Exploring the document hierarchy using a TOC-style navigator. The notion of descriptive markup. Practical work with document markup has since matured the SGML community, and the use of SGML has evolved towards better information modeling, and an increase in the practice of content tagging . Because it is not HTML's idea to endorse the concepts of descriptive markup, based on generic identifiers definable by the information owners, HTML will never be suitable for content oriented markup, nor for any kind of document that may need to be re-used.