Drupal shows mobile theme on desktop
If you are using varnish in front of the your server, then it will completly cache you request, Mobile tools will not be able to determine the useragent is mobile or desktop to redirect the theme.

One of the solution is to determine at varnish level and redirect to a m.domain which always has a mobile theme attached to it.

Refer the following links


http://fangel.github.com/mobile-detection-varnish-drupal/
http://mobiledrupal.com/content/mobile-device-detection-varnish-0