Main Forum: http://www.phcorner.net/ I created an archive forum for it, as a sub domain: http://archive.phcorner.net/ Does this help my SEO or just Drop my rank? What I'm doing is good or bad? Please I need an expert advice. Thanks !
It is said that the domain sometimes influence the rankings of the main domain. But there are lots of forums that are using this kind of technique and don't see them having a problem, i think it's quite ok to have an archive.
I think it's a good idea to use sub domain for archive because it will remove low quality content from your main domain.