Explorer Windows special: the xml prolog
In Explorer 6 Windows, Microsoft implemented one extra rule: if a doctype that triggers strict mode is preceded by an xml prolog, the page shows in quirks mode. This was done to allow web developers to achieve valid pages (which require a doctype) but nonetheless stay in quirks mode.
This is the xml prolog. You should put it on the very first line of your document, before the doctype.
<?xml version="1.0" encoding="iso-8859-1"?>
--Peter Paul Koch, "Quirks mode and strict mode" on quirksmode.org
cross-posted: weblingo, webmasterguild