How to set Canonical HTTP headers for cross-domain html to html?
I have two sites, one old, one new. The old one is not updated with new content but the new one uses reviews and other content that is naturally enough regarded by Google as duplicate content, so I want to either 301 the old site or rel=canonical to the new site...
... but the old site is an old CMS and the meta fields are keywords, description, and that'a about it and I don't think I have a way of writing between the <head> tags.
I'm not sure I want to kill off the old site with a 301, so I'd like to set canonical links in htaccess, but typically htaccess is used for .pdf to html domain links and not cross domain html to html, so I can't find a How To.
Any help welcome, thanks.