SSI is enabled for all Demon Web Hosting accounts by default. To use the SSI features your web pages should end in a .shtml file name extension.
The exception to this rule is for the custom HTTP error files inside your /errpages folder.
Those pages are checked for SSI tags even with a normal .html file name extension.

Example to 'include' an ASP file
Example to 'exec' an CGI script and a system command
Example to 'config' and display the date
Example to 'echo' the environment variables
Example to 'fsize' and 'flastmod' the size and date of a file
Example to 'set' the title of a page and mailto settings using dynamic variables
Example of 'if', 'elif', 'else' and 'endif' flow controls
Example for using SSI tags in /errpages/404.html