So I have a website that has greate Search Engine rankings, and like 500+ html
pages.

I want to unify the header and footer into one file, but don't want to change the
.html file extension to a .php file extension for fear of an SEO hit. 

So I tried:

```
    <!--#include FILE="header.html" -->

```

And it worked on my server, is there a downside to this?

Like future updates to the godaddy server rendering my header/footer invisible ?