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Copy and paste this into a text file, save it as test.shtml or something like that, put it on your server and call it from a browser.
If it shows the date, ssi is enabled on your server.
When using addhandler, remember to make sure you only try to parse one lang/protocol for each extension. I have seen people try to get ssi and php both parsed for the .html extension, makes one heck of a mess. I use
.shtml // for ssi
.html // for php
.htm // for plain vanilla html