"Internet Explorer, using the Trident layout engine, almost fully supports HTML 4.01, CSS Level 1, XML 1.0 and DOM Level 1, with minor implementation gaps. It partially supports CSS Level 2 and DOM Level 2, with major implementation gaps and conformance issues. Full conformance to the CSS 2.1 specification is on the agenda for the final Internet Explorer 8 release. It has no support for XHTML, though it can render XHTML documents authored with HTML compatibility principles and served with a text/html MIME-type."
"Internet Explorer has been subjected to criticism over its limited support for open web standards and a major goal of Internet Explorer 8 is to improve support for such standards."
"Although each version of IE has improved standards support, including the introduction of a "standards-compliant mode" in version 6, the core standards that are used to build web pages (HTML and CSS) are sometimes implemented in an incomplete and incorrect fashion. For example, there is no support for the <abbr> element which is part of the HTML 4.01 standard, and there are bugs in the implementation of float-margins for the CSS1 standard. There are also some CSS attributes missing from Trident, like min-height, etc."