Well, you are using server side includes (SSI) there. The Phorum templates are PHP code. Unless you do some special filtering setup in an Apache2 server (so I'm talking about the hosting platform here, not Phorum), it is not possible to use SSI.
Since the templates are essentially PHP-code, you could make use of PHP constructions to include the build_top.shtml code from the template. However, that will not result in a functioning Phorum. The problem is that there are various pieces of code that *must* be available in the header for Phorum to function. Things like stylesheet references, javascript sources, the {HEAD_TAGS} and the meta refresh code are required to make things work.
Maurice Makaay
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