Google referral drop after setting preferred domain

[Aggie]

Hey all, After doing a lot of research, and verifying here in the forum, I set our site's preferred domain on monday. We had no preferred domain set for years, but we were already redirecting the non www site to the www one. So, it was evidently an oversight. The day after I set the preferred domain (Jan 29) our google referral traffic hit an all time low. Any other thoughts on the cause? Any ideas on why setting a preferred domain would be a bad idea? Our site is www.mnn.com. Thanks!! Lisa

[Aggie]

Thanks!  Follow-up info.  I looked a little deeper and noticed that after our CMS upgrade, we saw a loss in google.com/URL referral traffic.  If I understand that correct, that's the traffic that comes from a referral link someone pulled from Google.

I know we had a bunch of 404s that have since been rectified, but we haven't recovered. Is there a portion of GA tracking code attributed to google.com/URL that we may have inadvertently dropped?

Thanks for helping me peel back the pieces of this SEOnion.

[StreamlineMetrics]

I am assuming by Google Referral you are not talking about Google Organic or Google PPC, correct? (Some people may consider "Google Referral" to mean "traffic from Google including organic/AdWords" so I just wanted to ask to make sure I am understanding the question clearly)

Assuming you are talking about Google Referral traffic, did you notice any changes in Direct Visits or Organic Visits on the 29th? A big change in Direct and/or Organic on the 29th may mean that there's simply a change in the way your analytics tool is tracking traffic sources.

If the only thing that has dropped was Google Referral traffic, then I think that Google's new Image Search is likely to blame. Google Image searches used to be tracked as Google Referral since the webpage was loaded in the background, whereas the new version does not load the webpage and thus is not tracked by Google Analytics/web analytics as a Google Referral visit. If this is the case, then it's likely it's simply just a coincidence that you noticed the drop in Google Referral traffic the same day the new Google Image Search was made available for a lot of people.

Here's a blog post showing similar declines in visits - http://www.webpronews.com/image-search-changes-google-said-would-be-good-for-webmasters-might-be-hurting-some-sites-2013-01