Canonicalization

This is a very techie subject, but you should know that search engines see two similar, but not identical URLs as different pages for the purpose of indexing those pages (that is, including them in their search results).  More simply?  A search engine thinks that http://www.semesq.com and semesq.com are two different pages, even though the content is exactly the same.  (Check out his post for more information: Canonicalization Update).

As a practical matter, you want to make sure that each URL has unique content or, when its the same content, have the search engine directed to only one page.  The best approach is using a permanent (301) redirect: sending the search engine to the page you want it to go to.  Here’s a discussion on how to do it: Permanent Redirects Using .htaccess file.