Staying Logged in Across Subdomains
How can I make it so my users stay logged in to the site if they transfer over to a sub domain? I have separated my site into two subdomains as I didn't see any way to have two different eCarts on the same domain that can be processed by a single checkout, plus it gives a more focused site for SEO, though it would be nice to have the one checkout if there was a way and it would be saved across the subdomain.
www.cis-prints.com
printing.cis-prints.com (under construction now)
Thanks