What you are trying to do is a responsive page. That is also called the 'mobile first grid system' because you make it fit the small screen first, then you only add new elements to the classes in media queries as you move to bigger screens.
This should get you started: http://css-tricks.com/resolution-specific-stylesheets/ http://css-tricks.com/css-media-queries/
And just google around the subject of 'media queries' and 'responsive web page' and you should find all the info you need.
Good luck!