If the page is well designed, you should be able to answer these questions without hesitation: What site is this?; What page am I on?; What are the major sections of this site?; What are my options at this level? (Local navigation); Where am I in the scheme of things?; How can I search?.
Don’t make me think
Being an expert in online usability Krug gathered his experience in a wonderful book. This summary of key thoughts will help you to remember most important principles and laws.