There are bunch of /_vti_xxx/ directories and files in my public_html directory. Can I delete them?

If you log in to your site with FTP or Telnet and find some directories (for example, _vti* ) and files (for example, .htaccess ) that you did not upload, DO NOT delete them. These are FrontPage Server Extensions components. You will damage the FrontPage support for your web site if you remove them. If you accidentally delete them, please submit a service ticket at Service Centre and we will re-install the FrontPage Server Extensions for you.