Responsive Design

One of the biggest changes to web design, likely since its inception, is the need for 'responsive design' - a fancy term that just means that a website has to be both functional and presentable on a wide array of device resolutions and orientations, ideally without regard to vendor or other device-specific settings.  Basically a website designed in this way should look and work great on a phone, a tablet or a desktop screen, and nothing should be lost when moving between these formats.  Sounds simple, right?