More about the "Quick Statistics"
= Index DOT Html by Brian Wilson =

End Tags | Standards Details | XHTML Modules
CSS 'Display' Type | CSS Mapping | Default Rendering
Main Index | Element Tree | Element Index | HTML Support History
End Tags
A document containing markup information actually describes a hierarchical "tree" of information, with imaginary branch points created by markup elements (also known as "tags".) Each continuous run of text content between the HTML elements is a "leaf" of one of these element branch points (meaning it has no children or branches from itself.)

You should already know from past experience that some HTML elements are not required to have an end tag - in other words, end tags are required if an element will contain anything inside it (such as text content or other elements.) If the element has nothing inside it, it does not need a closing tag.

The rules of HTML and XHTML allow elements to be defined as requiring [listed as "Required" in this section] or not requiring end tags [listed as "Optional."] In the case where an element will never have content, an end tag may be prohibited in the markup language's definition as well [listed as "Omitted" here.] Hopefully you aren't TOO thoroughly confused now. ;-}
Standards Details
The HTML 4.0 Recommendation is different than previous standards. In older versions of HTML, the language was defined in a single DTD, with only a few elements being deprecated. The deprecated elements could be "switched off" if the DTD was invoked in a "Strict" mode.

HTML 4.x has taken a different direction. The W3C is making a strong move to obsolete most of the presentational elements and attributes that have proliferated from browser makers since the language began. These constructs have been moved to Cascading Style Sheets (CSS) instead.

HTML 4.x DTD Types
To move from current common authoring practice to a new, more restrictive way of doing things would just be too drastic a move to succeed in practice. So, the W3C has broken HTML into two distinct modes: "Strict", and "Transitional" markup. Each of these modes is given its own DTD, where the Strict mode confines authors to using the HTML elements that impose structure only (the original intention of HTML) and rendering rules are specified using CSS. The Transitional mode, on the other hand, allows authors to use the markup they have been using all along together with the new functionality of HTML 4, and still have it all be "legal HTML."
XHTML Modules
In April 2001, the "Modularization of XHTML" document became a W3C recommendation. This was an important step in the further development of XHTML as a living, breathing and adaptable standard; it breaks down the pieces of XHTML 1.0 in to discrete areas of functionality. This will allow XHTML to be more easily extended in the future. Perhaps more importantly it will allow XHTML to be implemented in pieces on specialized platforms that have not been able to fully implement all of XHTML in the past because of various constraints and requirements (consider the case of a browser on a cell phone.) The extensibility of modularization can also be useful for future rendering needs that can not yet be imagined.

Core XHTML Modules
These modules are required to be present in any XHTML DTD variant.
Structure, Text, Hypertext and List modules

Other XHTML Modules
  • Text Extension (Presentation, Edit and Bi-directional modules)
  • Forms (Forms and Basic Forms modules)
  • Table (Tables and Basic Tables modules)
  • Image
  • Client-side Image Map
  • Server-side Image Map
  • Object
  • Frames,
  • Target
  • Iframe,
  • Intrinsic Events
  • Metainformation
  • Scripting
  • Style Sheet
  • Style Attribute
  • Link
  • Base
  • Name Identification
  • Legacy
CSS 'display' Type
In CSS, an HTML element is usually one of two basic 'display' property value types - "inline" or "block." There can, of course, be deviations from these values, but "inline" and "block" rendering behaviors are the two major categories that are given the greatest amount of documentation in the CSS standards. These two display types are the critical components of the CSS box model and are vital in determining a page's visual rendering.

The 'display' values for this field were taken primarily from CSS2 Appendix A: "A sample style sheet for HTML 4.0", originally created by Todd Fahrner. "Display" types for elements not present in that list were extrapolated based on known behavior and comparisons to elements that ARE in the list.
CSS Mapping
One of the major goals of HTML 4 was to move away from having presentation details in HTML itself. These rendering properties were to be shifted to CSS. This field attempts to describe which CSS properties and/or behaviors can be used to take the place of HTML-based rendering details. Mappings listed here come from a number of sources, including CSS2 Appendix A: "A sample style sheet for HTML 4.0 " originally created originally by Todd Fahrner, as well as known default renderings in the popular browsers.
Caveat: As mentioned in CSS2, Appendix A:
"The full presentation of some HTML elements cannot be expressed in CSS..."
Default Rendering
This field attempts to describe the typical initial rendering (visual or otherwise) of the element/attribute in the major browsers reviewed. This does not take into account any user style sheets or other modifications the user may have made to their settings. It also may not completely describe the rendering behaviors of ALL the reviewed browsers - it is just an attempt to characterize a so-called "default effect" that most users will likely experience.
Official Documentation
This entire website attempts to make the standards for HTML more accessible, but sometimes you just need to go to the source itself. These links are here to easily link you to the definitive statements on each of these elements if you desire more information.

Boring Copyright Stuff...