HCI is a fundamental and multidisciplinary research area. It is fundamental to the development and use of computing technologies. Without good HCI, computing technologies provide less benefit to society. We often fail to notice good HCI. Good HCI passes us by without comment or surprise. The technology lets you do what you want without causing you any further work, effort or thought. You load a DVD into your DVD player and it works: why shouldn't it? You take a photograph with your digital camera and without any surprise you easily transfer and view these on your computer. You seamlessly connect to networks and devices with a common interface and interaction style. Yet when HCI is wrong the technology becomes useless, unusable, disrupts our work, inhibits our abilities and constrains our achievements. Witness the overuse and inconsistent use of hierarchical menus on mobile phones; or the lack of correspondence between call statistics on the phone handset itself and the billed call time on the account bill; or the lack of interoperability between file naming conventions on different operating systems running applications and files of the same type (e. g. the need for explicit filename suffixes on some operating systems). Those programmers, designers and developers who know no better, believe that HCI is just common sense and that their designs are obviously easy to use.