I've recently bought some .mobi domain names and wanted to get things right, mark-up wise. Here's what I've settled on and the problems it causes.
First I change(or is it add?) the content-type response header, application/xhtml+xml;charset=utf-8. In this case with ColdFusion:
<cfheader name="content-type" value="application/xhtml+xml;charset=utf-8">
Then I add the following DOCTYPE and html name space.
<!DOCTYPE html PUBLIC "-//WAPFORUM//DTD XHTML Mobile 1.0//EN" "http://www.wapforum.org/DTD/xhtml-mobile10.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Page title</title> </head> <body> <h1>Page title</h1> <p>Paragraph</p> </body> </html>
This seems to work quite nicely except when I go to view the page in IE7 and I get prompted to download the file. I'll look into that another time.
Another thing to take into consideration is caching. With this is mind I use the following:
<cfheader name="expires" value="#GetHTTPTimeString(DateAdd('d', 1, Now()))#"> This is a nice tool to check your .mobi pages for problems. Then of course there's the validator we all use and how one of my .mobi sites turns out.