Tracking codes are an important part of Web Analytics. They are used by every single analytics tool. I recently came across a problem with how Google handles these tracking codes.
Here is what I have set up. We run the site RV Trader. The site lives at rvtraderonline.com. We also own the domain rvtrader.com, which we have set up with a 301 redirect to rvtraderonline.com. Recently we wanted to know how many visitors were accessing our site by going to rvtrader.com and being redirected to our main site. What I did was set up a tracking code on the redirected URL, using the query string parameter ?zmc=rvt. Now whenever anyone lands on the url rvtraderonline.com with that tracking code I will know 100% that they came from rvtrader.com since this is the only place where this tracking code exists. Pretty simple stuff.
I have been using ?zmc= for a long time now, and have it set in Google Webmaster Tools to ignore this parameter. For those who don’t know, there is a place in Webmaster Tools where you can tell Google what tracking codes that they should ignore. I have it set up to tell Google that it should not index any query string parameters that contain ?zmc=. I just double checked it and I do see that it is still there.
Then today we take a look in Google and what do I see:
How many of my other tracking codes have been indexed? Can I trust the reporting of any of my Omniture SiteCatalyst tracking code reports now? How many other analystics customers are going to have this problem? Is Google indexing tracking codes from any other Web Analytics tools?
If you are noticing any abnormalities in your tracking code reporting this may be why.