Serving XHTML with a MIME TYPE of text/html is wrong.

The whole point of XHTML is that it’s XML so that you can benefit from namespaces and the like.

In PARTICULAR, ‘text/html’ is NOT suitable for XHTML Family document types that adds ELEMENTS and attributes from foreign namespaces, such as XHTML+MathML [XHTML+MathML].

Two choices:
1. XHTML 1.0 SERVED as application/xhtml+xml to conforming UAs, and text/html to Internet Explorer
2. HTML 4.01, served as text/html 
XHTML 1.1 is not an OPTION because it mandates a MIME type of application/xhtml+xml which is incompatible with Internet Explorer

Serving XHTML with a MIME type of text/html is wrong.

The whole point of XHTML is that it’s XML so that you can benefit from namespaces and the like.

In particular, ‘text/html’ is NOT suitable for XHTML Family document types that adds elements and attributes from foreign namespaces, such as XHTML+MathML [XHTML+MathML].

Two choices:
1. XHTML 1.0 served as application/xhtml+xml to conforming UAs, and text/html to Internet Explorer
2. HTML 4.01, served as text/html 
XHTML 1.1 is not an option because it mandates a MIME type of application/xhtml+xml which is incompatible with Internet Explorer