Responsive design is a method of applying different sets of display rules  to elements of a website based on the size of the viewport availale.

These rules are applied via Cascading Style Sheets ( CSS ) and can affect the appearance, position, size or visibility of specific elements such as navigation, sidebars, pictures and the main content.

A single code base is created for the website rather than building a different website to be viewed on mobile phones, tablets and desktop computers.

Responsive design isn’t just a technical issue. A good responsive design requires design decisions to be taken to determine which elements to change as the viewport changes.

To see an example of responsive design in action, visit www.smashingmagazine.com with your web browser maximized. Now slowly resize the window until it is as small as it can go. The layout changes as you do this and as the viewport reduces in size, different parts of the style sheet are triggered and applied to the layout.

Android Home Screen (image from WikiCommons)

Anrdoid is a free mobile phone operating system. It is based on the Linux operating system and was created by Android Inc, which was later purchased by Google.

The code for the Android operating systems is now open source and overseen by the Open Handset Alliance. Google is still seen as the main driving force behind the project.

Like Apple’s iPhone, Android mobiles support multi-touch interfaces  installation of new applications on the phone, many of which are free of charge.

Most Android devices are made by HTC who were the first mobile manufacturer to adopt the operating system.

A QR code is like a bar code. It can be read by a mobile phone with a camera. The mobile device must have a QR reader installed on it.

The QR code usually contains  a web site address and will automatically connect the mobile phone user to the address of the web site contained in the code. However up to 3 kilobytes of information can be stored in a QR code which is about 3000 text characters.

This picture shows the QR code for the address of this web site.

QR codes are used on advertising and on product packaging so that people can quickly get more product information via their mobile phone.

QR stands for Quick Response and is a type of bar code that was invented in Japan where they are very common. They are becoming more common in Europe as well due to the growing use of mobile devices to access information on the web.

They can help to transcend language barriers, as web site addresses are all written in latin script. However,  the majority of world's population do not use a latin script in their native language. QR Codes help in this respect as no keyboard input is required and they are placed in context, on the product or near a service.