Guys, I've a real niggly problem and I don't know what to do.

I'm currently working on version 3 of Poplicious.Com. I want to include a community in it, and have bought and set up vBulletin for that purpose, but not opened it yet while I finalise the new site design and the forum templates.

Now on my new design, I'm using a very clever ad management system called AdCycle that uses a mySQL database to track and deliver ads. The ads are put into the pages by calling the script in an SSI call. All the pages of my site have the .shtml extension, as my the SSI calls won't work without this extension.

The thing is, I want to run some small ads on my forums, but of course because all the vBulletin pages have the .php extension they're not recognising the server side includes.

Is there another way to deliver the ads? I've heard of iframes but i'm a little dubious cos i'd heard they're not fully cross browser compatible. If a browser doesn't support them, does it just ignore the tag or go horribly wrong? Is changing vBulletin's default file extension possible? I don't know PHP so if it's complicated i'll not try it.

Any help here would be greatly appreciated.