Incompatibilities

The Internet Explorer way IE provides limited support for XML display with CSS1, as well as support for XML display with its own flavor of XSL. IE also provides 'data islands' inside of HTML documents, though this approach uses an illegal (in XML) element named 'XML'. IE includes DOM support as well, but no support for XLink.
The Netscape 6 way Although it's been slow to catch on, Netscape 6 supports XML plus a large chunk of CSS1 and 2, DOM, and simple links from XLink.
The Mozilla way Mozilla has provided the core of Netscape 6, but its own releases add support for MathML, SVG, and XSLT.
The Opera way Opera supports the display of non-Unicode XML documents using CSS1 and 2. Its DOM support is still in development, but some XLink support is possible through its extensions to style sheets.
The overlap XML 1.0 (in a limited set of encodings) and most of CSS1 appear to be all that is available. This is mostly adequate for documents, except for tables. HTML must be used for links.