Remember the XML specification is still relatively new, so a lot of what you see now is experimental, and because the potential number of different XML applications is unlimited, no single browser can be expected to handle 100% of everything.
Some of the generic parts of XML (eg parsing, tree management, searching, formatting, etc) are being combined into general-purpose libraries or toolkits to make it easier for developers to take a consistent line when writing XML applications. Such applications can then be customized by adding semantics for specific markets, or using languages like Java to develop plugins for generic browsers and have the specialist modules delivered transparently over the Web.
- MSIE5.5 handles XML but currently still renders it via the HTML model. Microsoft were also the architects of a hybrid (invalid) solution (islands) in which you could embed fragments of XML in HTML files because current HTML-only browsers simply ignored element markup which they didn't recognize, but his has now been superseded by XHTML. MSIE includes an implementation of an obsolete draft of XSLT (WD-xsl): you need to upgrade it and replace the parser (see http://www.netcrucible.com/ for details).
- The publicly-released Netscape code (Mozilla) and the almost indistinguishable Netscape 6 (there is no v5) have XML/CSS support, based on James Clark's expat XML parser, and this seems to be more robust, if less slick, than MSIE. Mozilla 0.9 is reported to have some XSLT capability.
- The authors of the former MultiDoc Pro SGML browser, CITEC, joined forces with Mozilla to produce a multi-everything browser called DocZilla, which reads HTML, XML, and SGML, with XSL and CSS stylesheets. This runs under NT and Linux and is currently still in the alpha stage. See http://www.doczilla.com for details. This is by far the most ambitious browser project, and is backed by solid SGML expertise, but seems to
be rather a long time coming.
- Opera now supports XML and CSS on MS-Windows and Linux and is the most complete implementation so far. The browser size is tiny by comparison with the others, but features are good and the speed is excellent, although the earlier slavish insistence on mimicking everything Netscape did, especially the bugs, still shows through in places.
See also the notes on software for authors and developers, and the more detailed list on the XML pages in the SGML Web site at http://xml.coverpages.org/.