Are sub domains treated as unique domains by the search engines? It seems that a domain with a general name could be used as the top level domain while the sub domains could be used for specific topics. Are they indexed separately? Regards, Tony
Google uses clustering to return results from a given domain: http://www.mattcutts.com/blog/subdomains-and-subdirectories/ Suppose you own the domain tools.com. On www,tools,com you have a great tool for helping me pick out a widget, but you also have the subdomain widget,tools,com which lists all the types of widgets you sell. If I search for widgets, Google will probably return two results for your domain: one to the widget selector, and one to the page on your subdomain listing all the widgets you sell. Google doesn't pay much attention to the fact that one reslt is a subdomain because ultimately all the content is part of tools.com. Subdomains and subfolders are simply ways of logically organizing your content.
They are indexed separately. Now, if you have a series of subdomains that all represent different topics related to the central theme of a well-established site, it can really help your rankings. Domains with specific topic keywords in them are usually better ranked to start with, and subdomain names are no exception. If you can name your subs so that they serve as descriptive words that go well with a descriptive top-level domain, you'll have an easier time with that portion of SEO. As an example, I host a couple of blogs as subdomains from my primary site. I didn't take a lot of care in naming the subs, but that's a result of my personal preference for specific names, and less a consequence of caring very much about keyword optimization. Anyhow, good luck with your sites!