[Lachlan wrote: IE has no native support for XHTML at all.] So it's not "native" support but there _is_ support. How can you tell if there is support, well, you do test-cases. If one can produce a test-case of valid XHTML served as HTML to IE and IE parses it correctly, then there is support. Why should we care if IE use an SGML or an XML parser to process the markup? The main thing is that markup is parsed correctly and there is no data loss. How can IE do this reliably? Because valid XHTML markup written to comparability guidelines is a sub-set of HTML.