I am looking to start a free website hosting campaign. I was wondering if there was a way to automatically place ads on all .html pages using .htaccess.

You'll prolly be better off using mod_rewrite I'd recon :)

How would I do that?

Lots of tutorials out there...

Well where can I find one?

:D you can find them by useing google. it's a search engine :D

mod_rewrite?

I think your confused. mod_rewrite changes the url not the page.

Use mod_layout search google for it.