MarkOly - 5:35 pm on Jun 30, 2013 (gmt 0)
Run Xenu LinkSleuth over the site and check for errors.
Also construct a text file list of "good" and "bad" URLs. Duplicate the whole lot for both non-www and www versions. In LinkSleuth set the scan depth to the lowest possible then import that list of URLs and check you get the right results.
Well I ran Xenu a couple days ago and got it down to no errors. So there's no bad URLs to add. But I did what you said and duplicated all the www versions as non-www and ran that list thru at depth of 1. That came out with no errors. The non-www were all redirected properly to www versions. Is that the point of doing this? To verify that the 'non-www to www' rule is doing its job? Also, why add the bad URLs to the list? Wouldn't you want to fix the errors first?
Now that I think about it, maybe I can use Xenu to test some of my other rules, once I add them - like htm and html to extensionless. I ran my old list of .htm URL's through and they all look to be redirecting without error.
The one error that persists is for the USPS Express Mail Service Commitment page I have posted on my Shipping support page: [postcalc.usps.com...] It always reports: error code: 503 (temporarily overloaded). I wonder if Google sees that as a broken link? It's strange. The link works. But it always reports as 503.
I need to spend some time torture-testing with different error combinations using web-sniffer.net and awebguy's HTTP Response Header Checker. I know that before I made all these changes, I spent some time doing that and I was very surprised at how many error combinations resulted in 200-responses that shouldn't have.