discordo do ponto 5, não o considero um erro mas uma opção, e pela minha experiencia, vejo as pessoas a clicarem mais depressa no pequeno botão X para fechar do que no grande botão para retroceder.
5. Do not open new browser windows: I used to do that on my first websites. The logic was simple, if I open new browser windows for external links the user will never leave my site. WRONG! Let the user control where he wants the links to open. There is a reason why browsers have a huge “Back” button. Do not worry about sending the visitor to another website, he will get back if he wants to (even porn sites are starting to get conscious regarding this point lately…).