On this server does not exist file-type-name 'index.shtml' in DirectoryIndex , and user do not have any permission adding the file type 'shtml' in '.hcaccess file'. If a host user wish to use SSI and let his guests be able to omit typing full file name (index.shtml) after domain name, (i.e. type 'oebashi.clinic' instead for type full 'www.oebashi.clinic/index.shtml') this file is nescessary in root directory, not to be forced to jump into server's default index page.