Will Blog Dilute Main Site Content?

how can you prevent content dilution?

[backdraft7]

This is probably an old question, but here goes...

I have a main site at www.xyz.com
My blog is at www.xyz.com/blog/home
I also have a subdomain set up as blog.xyz.com

My question is: will excessive blogging dilute the content of my main site? and if so, is there a way to prevent this? (other than deleting the blog).

TIA

[phranque]

is there any duplication of content between your main site and the blog?

My blog is at www.xyz.com/blog/home
I also have a subdomain set up as blog.xyz.com

do the subdirectory and the subdomain both serve the blog content?

[backdraft7]

On my server, when you set up a subdomain, it maps to www.xyz.com/subdomain so both that and subdomain.xyz.com are the same place...do I need to tell the search engine to use one and not the other?
There is no exact content duplication between the main site and the blog...just that I sometimes post slightly of topic stuff that I was thinking might dilute my overall niche.

[phranque]

do I need to tell the search engine to use one and not the other?

yes!
it's called canonicalization and you do this by using a 301 Moved Permanently status code and a Location: header referring non-canonical requests to the canonical url.
if you are on an apache server you can use mod_rewrite for this purpose.

i assume the subdomain is your canonical domain for the blog, but if you are using the subdirectory i would suggest dropping the /home from the url path as that is meaningless and worthless.

also, by crosslinking relevant pages on your blog and the main site you will likely be strengthening rather than diluting your content.