The Web server must detect that a file contains server-side include commands before processing the file. By default, the Web server is set up to process files with the .stm, .shtm, or .shtml file name extensions. You can disable the processing of server-side include directives for the entire Web server, for a Web site, for an application, or for an individual directory.
To enable server-side includesYou can add additional extensions; see Setting Application Mappings.
To disable server-side includes
If the Web server receives a request for a page with the removed SSI file name extension, it will not process server-side include directives within the page.