<p>I'm specifying my doctype as xhtml strict, but it's being sent over the wire as a content type of text/html.  I'd like to specify that the content type is application/xhtml+xm, but I can't figure out where, or if, I can configure this from within my application</p>

You can specify it in the @ page attributes section, like this:
```
```
<%@ Page ContentType="application/xhtml+xm" %>
```
```
...more on
MSDN
.