This has nothing to do with Piwigo, but all about web server setup. If your root directory is in http://www.xxxxxx.se/ and your piwigo is in http://www.xxxxxx.se/piwigo, you need to create a redirect  page as in http://www.google.com/search?q=redirect … amp;aq=t.. Alternatively, just put piwigo in your root directory.