The original 960 Robots theme is based on a 960 pixel grid. It has container and grid classes with widths declared in pixels—an absolute metric. In this lesson, we will take a first step in implementing a responsive design: converting absolute units to relative ones. We'll begin this process by editing the 960.css file, which contains the width declarations for our container and grid classes that make up our site's layout. Using the target ÷ context = result formula, we'll convert widths declared in pixels first to ems, then to percentages, with a little nudge of the decimal point over two places.
With our layout's container and grid classes using relative widths declared in percentages, we'll be on well on our way to making our site more fluid and flexible.