With the file extension SSI, HTML files are marked with server side includes (SSI). These are special html files that contain the instructions (script commands) that the web server should execute before the finished page is sent to the client, ie browser.
The instructions usually beginning with '<! -' are ignored by most servers on files ending in htm or html. A typical application is the integration of date and time.
The extension seems to be mainly used or recognized by Dreamweaver. Much more commonly used endings are shtm, shtml and sht.
SSI files can be used like html files in any text editor and web page editor, but they can only be used by SSI capable servers, for example Apache or Microsoft IIS.
Most often resolving problems with opening SSI files is very simple. Just install an appropriate program that supports such files. All of the listed programs support SSI files, but may vary in offered function and purpose. Some programs may be capable only of viewing contents of SSI files or offer file conversion options, but may not be capable of editing such files.
It is possible that although a compatible program has been installed on user’s system, it is not used by the system to open it. This may happen because no default application was associated with this type of files. To associate SSI files with given application, select "Open with" from drop-down menu (accessed by right-clicking on the file). Then select from the list the program or application you want to be used to open this type of file. If the Adobe Dreamweaver applications is not on the list, select "Browse" option in order to manually locate the directory where Adobe Dreamweaver has been installed.
Sometimes problems with opening SSI files may not lie with the application itself, but can arise due to other causes, such as: