The document discusses principles of usable web design from Steve Krug's book "Don't Make Me Think". Some key points are: 1) Users scan pages quickly looking for relevant information rather than reading thoroughly, so design for scanning by using clear visual hierarchy, conventions, defined areas, obvious clickables and minimizing noise. 2) Make important content no more than two clicks away, be consistent, speak the user's language, use whitespace and don't require extra thought processes. 3) Frustrated users will leave a site for competitors easily, so usability is important for retaining visitors.