Is it possible to use apache to add a line of code to every web page served either from a certain domain or the whole server? I know some might say to use SSI includes, but I need this done without making the web page authors alter their code.

Thanks

You can use mod_rewrite.

http://httpd.apache.org/docs/mod/mod_rewrite.html
:D

OK I'm trying to figure out how to do it via that documentation but I'm lost. Any more specifics to narrow how to do it down?

Thanks

I'd also take a look at ModLayout (http://software.tangent.org/projects.pl?view=mod_layout)