A surprising number of net surfers do not know how to use the back arrow on their browser. So, make sure you have navigation buttons on each page. If users are confused as how to navigate your website, they won't stay long. Have Useful Content On Your Website. Well, this seems obvious, but many sites overlook it.
People go to web sites because they want information.
Snazzy Flash animations are nice, but people are looking for information not dazzling graphics. Give The Site Focus. You have about five seconds to attract and keep a new person's interest. So, make it clear what the site is about. Don't hide important stuff two levels down.