Solution:
There is already twenty-twelve and twenty-thirteen theme available on wordpress.org
and both are responsive (mobile friendly) themes and you can modify and use them but also for WordPress
there are some plugins available as well, you can use any one but I suggest you to use wptouch, it’s free and better than others, IMO. I’ve used it for years for my blog but now I’ve managed to use a responsive theme.
If you install wptouch
plugin then whenever a visitor will visit your site with a mobile phone, WordPress
will use a mobile friendly theme by the help of wptouch
plugin but if you use a responsive theme then it’s always the same theme but layout will be changed to fit according to device’s screen size (desktop, tablet, mobiles) and it’s better than using a plugin like wptouch
, so if you can, use a responsive theme instead, search on Google for free responsive themes for WordPress.