Responsive design has been a big boom recently and it's still a mystery to some. Let's see just how easy it really is. Let's say you want to start simple with a normal desktop version of your website and one suitable for smaller screens like mobile phones. Let's start with something like the menu. You can create one menu and set it to display for large windows and make a compact menu, perhaps a dropdown, for smaller screens. This is where CSS Media Queries come in. In the HTML there can be two different menus created with only one set to display at a time.
Twitter Bootstrap, which was renamed to simply Bootstrap, is am amazing tool for web developers. It is now my favorite way to get a new site going. As a developer, I feel it is powerful and flexible, but not bloated. It is just the right tools for almost any project. Check out their official website here. It comes in a very light and simple package that includes: