Redirect to Last Page Visited
This script will redirect the user to the page where he left your site at the last visit. Redirect is only performed if the user enters the main page of your site from any other site. If the user enters your site by direct link from any search engine or another site, the redirect is not performed allowing the user to see the appropriate content.
Read more here
edit: Programming/Javascript/auto___redirect_to_last_page_visited.wikieditish...