HTML and CSS Reference
distance it from the tawdry reputation of DHTML despite being mostly
the same thing. Although the web had long been touted as a platform
for applications, the AJAX trend looked like it had a chance of making
that possibility a reality.
The competing standards
You may have wondered what the W3C has been doing in the decade
since HTML 4.01 was released. It has, of course, been working on
plenty of standards other than HTML , but it's also working on a
replacement for HTML4 . The W3C decided that the future of HTML
lay in XML . XML is superficially similar to HTML —documents, tags,
and elements all exist in XML , but it has two major differences:
XML parsing is much stricter than HTML . A few mistakes in an HTML
document will, in many cases, not even be noticed; the browser will
correct the errors as best it can and carry on. A single error in an
XML document causes the parsing to fail and an error message to be
displayed. The stricter approach allows browsers to be more effi-
cient, which is particularly useful on mobile and low-power devices.
XML is extensible. If you want to add new elements to your XML
page, you can do so. You describe those elements in a separate file
and link to it from your document. Your new elements are then just
as valid as any specified by the W3C .
The first step was to redefine HTML 4.01 as an XML standard.
XHTML 1.0 became a Candidate Recommendation in October 2000. It
contained no new elements or features; all the valid elements were
identical to those in HTML 4.01 . The only changes came from it now
being a dialect of XML . The plan was to extend XHTML in a modular
fashion by plugging in new XML dialects. Some of the better-known
XML dialects the W3C expected to be plugged in to XHTML were
Scalable Vector Graphics (SVG) , which became a CR in August 2000;
and M ath ML , an XML language for describing equations, which
became a CR in April 1998. The modular approach allowed different
technologies to be worked on at different paces.