I use Google personalized homepage to track the latest and greatest news. Google recently unveiled a new feature that puts a little plus next to stories. When you click on this plus, the article description slides out underneath.
So I clicked on a feed from CNN and noticed two blank image placeholders appeared and then quickly disappeared. I noticed this was also the case for my Slashdot feeds. So I examined the raw RSS feed on Slashdot, and noticed this:
<img src=”http://rss.slashdot.org/~a/Slashdot/slashdot?i=1sz5lq” border=”0″></img></a></p><img src=”http://rss.slashdot.org/~r/Slashdot/slashdot/~4/86854678″/>
In other words, whenever the feed is viewed by a reader that supports HTML (most readers nowadays), a 1×1 pixel image is displayed from the Slashdot server. This allows the server to track where feeds are being viewed from as well as any other information they can scrape such as your IP, the time, if when the feed was pulled, your username (on Slashdot), etc.
This technology is widely used in e-commerce for tracking clicks that lead to sales. While this is an obvious step, I had never really heard about this until now.
One unintended consequence of Google’s reader is that the pixel only fires if I click on the plus image. This means CNN et al. is able to determine if a particular viewer who looks at a description is more likely to come read the full article. It also means the pixel only fires by active user intervention, making the tracking feature largely useless. But then again, if users pinged 25 servers every time they loaded up Google, I think a lot of servers might begin to have problems. 🙂
If you didn’t already know of this, I hope this was an interesting read.