Forum Moderators: phranque
If you use DW's templates, your subdomain site will need its own templates in its own Templates folder. It will need its own images folders and its own css stylesheet. If you want the subdomain site and the main domain site to link to each other, use full http:// URLs for those links, because you are, in effect, linking to a whole separate site. Don't use any links from the main site to /subdomain/page.html, because then your site-root-relative links wouldn't work in your subdomain site.
Just to be safe, you could set up a redirect such that if someone goes to mydomain.com/subdomain, they will automatically be redirected to subdomain.mydomain.com. That will ensure that your subdomain site will always be served up by Apache as a stand-alone site, thus keeping your site-root-relative links correct.