Responsive Web design

Take a look at the following link and watch a very good video (25 minutes) about Responsive Web Design!
http://css-tricks.com/video-screencasts/102-braindump-on-responsive-web-design/

 

                                            jsfiddle.net 

In the above picture you can see jsfiddle.net, an online editor for the web, which allows you to see how your code runs in action. Really very helpful!