A file extension that is also sometimes known as SSI, SHTML is an HTML file that includes server instructions or server side includes and similar to an ASP file. This file is used to associate files that include server instructions so all files load as fast as possible.
A server administrator may set the name of the file extensions to anything; however, the files are commonly either .SHTML or .SSI. It is also possible for the administrator to allow all files to include executable code; however, enabling this can cause the server to load slower since the server perform additional tasks for every file opened.
A web page visitor counter or dynamic content such as a web page calendar are good examples of why a user may want to embedded instructions on his or her web page. Below are some examples of how a user may implement a Perl script into their web page or echoing local information to a web page.
<!--#exec cmd="cgi-bin/mycounter.cgi" -->
<!--#include virtual="/cgi-bin/mycounter.cgi" -->
<!--#echo var="DATE_LOCAL" -->
The first line is the most common method for executing code from the server. However, because of security risks, an administrator may disable this feature on the server. The second line is another example and usually the alternative to the exec cmd. The third example is just another example of how a server may be setup to execute a file. Finally, the last line is a method of echoing the local date and time to a web page.
Additional questions regarding the setup or configuration of SHTML or SSI should be directed to your Administrator or ISP. If you are the administrator or are attempting to enable SSI on your server, we recommend you refer to the documentation of your web server.