Well no one knows for sure. If I had to take a guess it might be a phrase (Google Test Ad or GoogleTestAd) used by publishers to see how their ads show up in the results or some kind of rank checking software. I came across a post today from the blogosphere talking about it. Apparently last month the phrase was in the top 30 most popular phrases and gained about 40,000 searches last month. Prime for the picking it seems for some people. There has been a rush for some to create websites and scrape some content in order to capitalize on the traffic with Adsense or by selling third party SEO software. If it does get that amount of traffic, it's questionable whether or not it would actually convert to a sale or click for anyone. But people are interested. If you haven't heard about it, then don't worry its not exactly exciting but with anything its gained some interest lately. As far as I can tell no is able to figure out what it is for.
One site in particular googletestad.net claims "Googletestad page developed for no reason at all. It's a popular keyword in need of a home." Hmmm...
The top sponsored ad on the page looks like the following:
Its family safe!
To see what the commotion is about, check out the search "googletestad".