The billboards loomed over America's highways and byways displaying three pictures. In the first scene, the frowning housewife held up a pair of grubby trousers for all to see. Second, she put them in the washing machine and poured from the sponsor's distinctive box of soap powder. In the last picture, she displayed her sparkling clean garment and her radiant smile across the consumer landscape.

She sold millions of dollars worth of laundry detergent.

It was the middle of the 1950s, and billboard advertising was in its prime in the U.S. The detergent promotion did so well that the sponsor decided to expand it to international markets and chose a Middle Eastern country to experiment with adapting the advertisement.

The billboards had been very successful, so the ad agency confidently prepared the new design by substituting Arabic for English in the name of the detergent. Ad executives bought their display space and launched the campaign. It was a resounding failure.

Why? When the designers moved into new territory, they ignored three important principles: designing for user characteristics, designing for the user experience, and designing for context.

They disregarded user characteristics when they failed to replace the image of the quintessential U.S. housewife with a face and clothes familiar to the Middle Eastern audience. They ignored user experience by maintaining the left-to-right orientation of the three pictures in the display. Unlike readers of English, Arabic readers scan from right to left. Consequently, Middle Eastern consumers saw the smiling woman use the sponsor's soap and end up frowning at a grimy pair of trousers.

Finally, if the designers had analyzed context, they would have found that billboards for advertising were not common in this Middle Eastern country at the time. They might have chosen to promote their product through the more popular medium of magazines and newspapers.

The lessons learned from the above experience are at the heart of this book. The absolute requirement to design for the user and to design for context is the basis of usable web design and the foundation of web design's connection to usability engineering.

The practice of interaction usability engineering is rooted in the field of Human Computer Interaction (HCI), which itself combines three distinct methodological approaches. HCI methodologies derive from the science of behavior, computing technology, and design. The science of behavior emphasizes the quality of the empirical methodology used to discover important insights about interaction behavior. Computing technology models and invents technological solutions for human interaction problems. For design, methodological power resides in the designer's virtuosity of expression. It is from this methodological context--combining the methodologies of discovery, invention, and designÑthat the practice of interaction usability engineering emerged.

In this book, I relate and apply interaction usability practice to the design of web pages, web sites, and web applications. Because web usability design is grounded in HCI methodologies and principles, I will begin with a summary of HCI history and principles and how these are related to the practice of web usability.