Book on User-Centered Web Design Available Online for Free

In this book, we primarily address universal usability at the functional layer, focusing on the challenges of designing pages that are accessible and usable on different devices by diverse users. We concentrate on the functional layer because, without it, the other layers are irrelevant. An intuitive interface and informative content are useless if the basic functions of a site don’t work. Like a car that doesn’t start, a Web site that does not function is of no value to the user. Link