Creating a web application means that you cannot assume any given display size. In fact, the user may change the browser's window size, and your application should somehow respond to that, rearranging whatever is shown on screen to better work with the current screen dimensions. If your web application is capable of this reorganization, it's said to be responsive. Today, given the extreme range of devices with browsers (ranging from small phone handsets to very large flat screens), doing responsive design is really a must, so in this section we'll see how to work with this. I'll assume you are already aware of CSS concepts such as grids and columnar designs; please read up on them if not.
To allay a common, fairly obvious question, if you are aware of current trends in CSS, you may ask why aren't we using...