A modern website cannot exist anymore nowadays without a powerful mobile version compatible with various types of smartphones and mobile platforms. I will give guidelines about general web mobile design process and problems (content strategy, touch-screen issues). I will present some special features of mobile devices that must be considered (screen sizes, viewport). I will explain the main different possible approaches for Drupal mobile website building (dedicated modules, Responsive Web Design and CSS3 media queries, Cloud services...) and I will show some cases studies.