Using plain language in government websites; free book on website design and usability

Free website usability guidelines book, from U.S. Department of Health and Human Services

Throughout your Web design or redesign project, you should take advantage of what is already known about best practices for each step of the process. The Research-Based Web Design & Usability Guidelines (PDF, 20.64MB) brings you these best practices compiled through an extensive process of research and review. (From usability.gov)

You can also download specific sections of the book:

• design process and evaluation (PDF - 1.9MB)
• optimizing the user experience (PDF - 9.1MB)
• accessibility (PDF - 2.4MB)
• hardware and software (PDF - 2.8MB)
• the homepage (PDF - 12.1MB)
• page layout (PDF - 21.9MB)
• navigation (PDF - 13.1MB)
• scrolling and paging (PDF - 4.5MB)
• headings, titles, and labels (PDF - 7.8MB)
• links (PDF - 17.1MB)
• text appearance (PDF - 11.2MB)
• lists (PDF - 6.6MB)
• screen-based controls (widgets) (PDF - 15.1MB)
• graphics, images, and multimedia (PDF - 16.8MB)
• writing Web content (PDF - 11.0MB)
• content organization (PDF - 10.1MB)
• search (PDF - 9.1MB)
• usability testing (PDF - 1MB)