Choosing a mobile domain name
One of the hardest parts of building a mobile site is choosing what you’re going to call it. Not only do you have to choose a cool name for your URL, you also need to choose how you’re going to signify that it’s a mobile site.
The options are.
Standard practice for the Mobile Web is using the m subdomain. It’s short, so you don’t need to type in too many characters, it’s well used, and there are more sites using it than any of the other choices.