hello Would you please tell me which is better for seo, better result ? forum.mysite.com or mysite.com/forum thank you
I personally prefer forums.mydomain.com but really I don't think it makes much of a difference. Although I hear google considers subdomains different from the root domain... so that might be something to consider.
A few years ago the sub-domains seemed to have a strong influence with Google, have not seen it since. A well planed site structure (eg. categories and sub-categories) that is SE friendly and user friendly will repay you with excellent SERPs and fewer headaches in the future. Both will work fine with no preference to either, if you are planning on using an SSL it can be an additional fee to secure the sub-domain.