So far, we've adapted our layout to be flexible and fluid using relative units like percentages and ems, instead of absolute ones, like pixels. The problem is that smaller devices will often use resolutions much greater than the actual size of the screen size or viewport. So while our relative sizing is technically working, it's not going to be terribly useful or make our content more readable and accessible until we add an important tag to the head of our html template file: the viewport meta tag.
By adding the viewport meta tag to the head of our html template file, we're letting the browser know that we want the viewport size to be the size of the device, not some huge resolution more suitable for a 17" monitor, for example. This is a small but critical step in implementing a responsive design. Without it, our hard work of converting to relative units just isn't going to pay off.
In this lesson, you'll learn how to add a viewport meta tag to the head of all html pages using a special Drupal template file that we'll create. Then we'll step back and admire the results using our mobile emulation tools.