Mobile browser to be assigned different background I'm trying to get my site to operate differently depending on if the browser is a phone or a computer etc... I understand that this is most likely done using the sites.php file but I've been unable to get this working, and have an open question on SO about it.

Broad Question

This question is a little more specific and is to tied me over while I battle the broader issue out. I would like to remove the current background image when a mobile browser turns up. I thought something like the following would do it (same CSS file) 

body {
 background-color:blue;
}

@mobile {
 body {
 background-color:green;
 }
}


but this doesn't appear to make any difference when using my HTC desire using Dolphin.
I use Omega for that.

It's based on CSS media queries.