mime type and wordpress header

If specifying the Content-Type is important… and WordPress uses xhtml… why would the header.php file contain this:

<meta http-equiv="Content-Type" content="<?php bloginfo('html_type'); ?>; charset=<?php bloginfo('charset'); ?>" />

When generates this:

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />

if it should have or generate this:

<meta http-equiv="Content-Type" value="application/xhtml+xml" />

Anyone? I am testing my site on the mobiforge.com site and I have the mobile web pack installed and activated… I get good results, with a couple of exceptions, this being one.

I’m trying hard to understand it and get into mobile web design, so any enlightenment is greatly appreciated, thanks!