View http://www.456bereastreet.com/archive/201112/the_difference_between_widthauto_and_width100/
I like collecting links to various tips that help with responsive design techniques, and this is a good one. So much has to do with layout refactoring as various breakpoints are reached, and much of the time we’re working with the widths of many DOM nodes so as to reflow in the way we want. With a bit emphasis on mobile first development, we’re working from more restricted widths to those that increase in width, very often until we want to remove the width restriction altogether. Quiz: should you be using width:auto or width:100%?