Duplicate content + subdomain

[olly]

We serve images under a subdomain to improve page load performance:
images.ourdomain.com

However, I have just done a "site:images.ourdomain.com" in Google and I see that ALL of our content has been indexed under this subdomain too. Not ideal as now we are serving identical content under different subdomains.

I would imagine there are standard ways to fix this. We obviously want to proceed so that:
- we do not affect our organic rankings
- we prevent this happening in future

[bwnbwn]

Olly the only thing I guess is your whole site is loaded in the subdomain. Is this correct does the content in the subdomain return a 200 hearder response?

[tedster]

your whole site is loaded in the subdomain

Exactly the problem. Only your image files should be returning a 200 OK response from the subdomain, not the html files.

By the way - that is an effective strategy to allow browsers to multi-threading and speedup the page load. So don't give that up.

[olly]

Yes, the content under images.ourdomain.com loads identically as when accessed under www.ourdomain.com - we have just added a hostheader in IIS. So 200 OK responses are being returned in both instances.

Are you saying the way to proceed is:
* Issue 404's whenever anyone tries to access images.ourdomain.com/<content>.htm

BTW does it matter if the images are accessible under both domain and subdomain? Or should we issue 404s when trying to access www.ourdomain.com/<image>.jpg?

[bwnbwn]

olly Ted told ya the answer. All duplicate content needs to be removed from both sites. If the sub is only for images then that is all you should have there nothing else.

Now ya got to get all the duplicate content from under the subdomain out of the index. Not sure the best way there maybe it be best to just have them all 404 and sumbit a url removal in WM area for the urls indexed under the subdomain.