Nine days ago, I got a message Google Webmaster Tools:
Over the last 24 hours, Googlebot encountered 1 errors while attempting to access your robots.txt.
Well, but I don't have a robots.txt on that site, because robots.txt is optional and I want the whole site to be crawled. So why do I get this error message?
Perhaps of interest: The Google Webmaster tools home page lists www.realitybuilder.com and realitybuilder.com. I don't know how that happened, but realitybuilder.com redirects to www.realitybuilder.com, so it should not be necessary to have it listed. I now deleted the entry for realitybuilder.com. Could that have caused the problem?