Section I.3. HTML

I.3. HTML

In an otherwise fast-moving environment, it's hard to believe that the current Worldwide Web Consortium (W3C) document content markup standard, Version 4.01, was published in December of 1999. Since then, most attention has been paid to the XHTML effort (described below) as a replacement. In late 2006, however, W3C co-founder, Tim Berners-Lee, signaled the revitalization of HTML in parallel with XHTML. Whatever the future might hold, we must recognize the critical role that HTML 4.x has played in the evolution of content delivery on the Web and how authors construct content.

Many of the features that were new to HTML 4 were designed for browsers that make the graphical user interface of a web page more accessible to users who cannot see a monitor or use a keyboard (see "Web Accessibility Initiative (WAI)," later in this Online Section). The new tags and attributes also acknowledge that a key component of the name World Wide Web is World. Users of all different written and spoken languages need equal access to the content of the Web. Thus, HTML 4 included support for the alphabets of most languages and provided the ability to specify that a page be rendered from right to left, rather than left to right, to accommodate languages that are written that way.

Perhaps the most important long-term impact of HTML 4, however, was distancing a web page's content from its formatting (presentation). Strictly speaking, the purpose of HTML is to provide structural meaning to the content of a document. That's what each tag does: this blurb of text is a paragraph, another segment is labeled internally as an acronym, and a block over there is reserved for data loaded in from an external multimedia file. HTML 4 sought to wean authors from the once-familiar tags that make text larger, bold, and red, for example. That kind of information is formatting information, and it belongs to a separate standardization effort related to content style.

In the HTML 4 world, a content author indicates that a chunk of text in a paragraph is to receive emphasis based on that text's context within the document. The HTML standard, however, does not dictate whether the browser conveys emphasis through a bold or italic or green font. Instead, a separate style definition controls the formatting for an emphasized string of text. This separation of content and style allows the same content to be rendered differently for a variety of output devices. When emphasized text is viewed in a browser on a video monitor, the color may be green and the style italic, but when the same HTML markup is viewed through a projection system, it may be a different shade of green, to compensate for the different ambient lighting conditions, and bold, so it is more readable at a distance. And when the content is being read aloud electronically for a blind user, the synthesized voice speaks the tagged words with more vocal emphasis. The key point here is that the contentthe words in this caseis written and tagged once. Style definitions, either in the same document or maintained in separate files that are linked into the document, can be modified and enhanced independently of the content.

HTML 4 was also the first version of HTML to account for the role that client-side scripting was playing in the real world. Not only did <script> and <noscript> tags become part of the specification, but most elements that get rendered on the page had a basic set of scripting event handler attributes explicitly defined for them (onclick, onmouseover, onkeypress, and the like). If nothing else, these acknowledgments validated the idea of client-side processing instructions delivered as part of the document. It also allowed HTML-validating programs to accept attributes that link elements to script actions.

The long-term stability of the HTML 4.01 recommendation means that virtually every popular browser released since 2001 supports (or claims complete support for) the standard. Therefore, you will find satisfactory or better HTML 4.01 support starting with Internet Explorer 6 (Windows), Internet Explorer 5 (Macintosh), Mozilla 0.9.4, Safari (Macintosh), and Opera 4.