Joomla takes a big leap into the mobile space with a total overhaul of both its frontend design and administrator interface. With the adoption of the Bootstrap framework, Joomla! has become the first major CMS to be mobile ready in both the visitors and administrator areas. Now every website can have mobile friendly content for visitors and mobile friendly tools for administrators.
Joomla 3.0 is having responsive design will work on all handheld as well as systems .
From : http://www.joomla.org/3/en