Why don't SSI's work for me?

I'm trying to include one html file into another. I'm coding on the MAMP stack. I assume SSI's are automatically permitted. I type <!--#include virtual="header.html" --> in the body of one html file, the other file is called header.html, and they are both in the same folder. I even tried calling the file header.shtml instead. N开发者_C百科one of this works. It's frustrating.

The code isn't included. I'm including a form and a navigation bar, but they don't appear.

I assume SSI's are automatically permitted

That's a very big assumption. SSIs will only work if you've got mod_include loaded. You also need to enable the filter for the relevant files, e.g.

AddOutputFilter INCLUDES .shtml

...and of course ensure that Includes are not overridden elsewhere in the config.

Did you read this?