Is Google Webmaster tools Accurate?

[jimmyjohnson]

Is Google webmaster Tools data completely inaccurate, or am I just missing something? I noticed a recent surge in 404 errors detected 3 days ago (3/6/11) from pages that have not existed since November 2011.

They are links to tag and author archives from pages initially indexed in August 2011. We switched to a new site in December 2011 and created 301 redirects from categories that no longer exist, to new categories. I am a little perplexed since the Google sitemap test shows no 404 errors, neither does SEO MOZ Crawl test, yet under GWT site diagnostics, these errors, all 125 of them, just showed up.

Any thought/insights?

We've worked hard to ensure a smooth site migration and now we are concerned.

-Jason

[SL_SEM]

No problem, and good luck hunting it down

[jimmyjohnson]

Thanks Charles. Never would have have thought of AW Stats..and the WMT article was very helpful. Yes it is mostly annoying, since it's hard to explain to a client that errors "are not really errors" sometimes. They are attorneys and want specific explanations...until now this was un-explainable.

Thanks again.

[SL_SEM]

Do you run a log file analyzer like AW Stats? If not you should be able to set it up and have it build stats for you as long as you have your log files laying around.

The reason I ask is that AW Stats will show you what files on your site are throwing 404 errors specifically. It might be that it isn't a page, but a file that is referenced by multiple pages in your site that no longer exists. This would throw a 404 response, and depending on how your system handles 404's the google bot might be getting redirected to a 404 page when trying to access that file.

It's not highly likely, but I would check into that.

If you are concerned about the 404's causing problems for your rankings you shouldn't worry about it in most cases. Check out the article here for more details: http://googlewebmastercentral.blogspot.com/2011/05/do-404s-hurt-my-site.html

If it is just annoying you I would dig into the log files and see exactly when the 404 is being thrown, and what the file is that is doing it.