If you are looking through the code on your site and find a mysterious call to a javascript in the domain "cetrk.com," you may wonder what it is and if it is a malicious script or a hack.

 <script type="text/javascript" src="http://cetrk.com/pages/scripts/0001/3919.js"></script>

When I found it at the bottom of my home page, it looked like it might be something to worry about, so I started investigating. It took a while to find the answer, but it turns out that "cetrk" is a domain which used to host Crazy Egg Tracking scripts. Crazy Egg is a site that provides analytics reports. I had tested their tracking service several years ago, then forgotten to remove the script when I stopped using the site.