I noticed that there was a comment on Aaron’s blog SEO Buzz Box after an interview with me regarding sub domains. I want to clarify my view on sub domains and when it’s best to use them. About 4 years ago I would have recommended using sub domains on new sites any day of the week and at that time they worked perfectly.

However I believe that Google views sub domains as new sites, and it’s really clear when you look at blogspot.com. Just because the primary domain has a lot of power, doesn’t mean that the sub domains will have the same benefit. Would it make sense that you could simply add an account with a few keywords and then rank for it? Maybe on MSN, it does. Take a look at Cingular Ring Tones, a nicely spammed result set.

I have optimized many sites that have had sub domains for years and they do very well. This year I have added several sites with a lot of content, using sub domains. Where the primary TLD is extremely powerful and has 100’s of thousands of links pointing to it. I can tell you without a doubt that 3 sub domains that where added with millions of pages of content performed poorly at first and took months to build up. If I could have done it again from scratch I would rather have used a Folder based structure keeping the content on the primary domain.

There is a lot of talk that sub domains are dead and they will not rank. This is incorrect; I am constantly launching new sites on whole new domains and sub domains. I have had no problems what so ever getting sub domains to rank. Think about it, would Google use sub domains if they thought it was evil? Maps.google.com, etc.

You should not use sub domains that look like, my-cool-keyword.mysite.com. Not only will it not rank, but no one can remember it.