I\'ve noticed that in JSF 2.1.* my IE conditional comments are no longer working. Various characters are being replaced by HTML entities & invalidating the comment syntax.
Wrap it all in a <f:view> and define the namespaces there.
<f:view>
<!DOCTYPE html> <f:view xmlns="http://www.w3.org/1999/xhtml" ...> ... </f:view>
The entire JSF view is otherwise already implicitly wrapped in a <f:view>.