Yes, HostPapa does support server side includes.
SSI (Server Side Includes) is a simple server-side scripting language, generally used for the web.
Server Side Includes allow you to build a web page in pieces and have a visiting browser put all the pieces together. They are useful for including a common piece of code throughout a site, such as a page header, a page footer and a navigation menu. For example, you could build the header of a web page, store it as a single file and then use SSI to add that header to a web page when a browser loads it.
In other words, SSIs allow you to add dynamically generated content to an existing HTML page, as opposed to serving the entire page via a CGI program or other dynamic technology such as through a Content Management System (CMS) or database.
The main advantage of SSI is apparent when the site needs to be updated. An update to a SSI file will show up automatically on every web page that includes that SSI file. Going back to the SSI header mentioned above: if you add new information to that header, the new information would automatically appear on each page of the site. It’s much faster than if each web page had to be updated with the new information.
SSI is a great way to build consistency into your website so that all content uses the same fonts and styles. SSI can also be used to add small pieces of information, such as the current time or stock quotes.