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Hi nigel555,

I was thinking along these lines, but I was concerned it was too simplistic of an approach. I was sure I was missing something.

How do you feel about the approach outlined above by Irving?

Thanks for the help Irving.

So you think we should block the subdomains with robots.txt files and then use the URL removal tool to remove the "sites" from Google's index.

I have done a site: search looking for indexed URLs from the subdomains, but the searches were empty. Do you think I should still use the URL removal tool?

We have two subdomains that have been verified in Google Webmaster Tools. These subdomains were used by 3rd parties which we no longer have an affiliation with (the subdomains no longer serve a purpose).

We have been receiving an error message from Google: "Googlebot can't access your site. Over the last 24 hours, Googlebot encountered 1 errors while attempting to retrieve DNS information for your site. The overall error rate for DNS queries for your site is 100.00%".  I originally investigated using Webmaster Tools' URL Removal Tool to remove the subdomain, but there are no indexed pages. Is this a case of simply 'deleting' the site from the Manage Site tab in the Webmaster Tools interface?

I've found PageSpeed Insights (https://developers.google.com/speed/pagespeed/insights) to be very helpful. It offers suggestions on how to improve the performance of your site, based on the potential for improvement. By benchmarking your site against others in your industry (or top performers in other industries), you can compare not only the overall PageSpeed Score, but you can identify how the suggestions differ.

This enables you to identify possible competitive advantages/disadvantages. For instance, if you receive a high priority suggestion that your competitors have already implemented, you may be at a disadvantage; the severity of which dependent on the resources required to implement the suggestion.